diff --git a/accessible/android/DocAccessibleWrap.cpp b/accessible/android/DocAccessibleWrap.cpp
index fd8a5ae911d6..a9331bfc39da 100644
--- a/accessible/android/DocAccessibleWrap.cpp
+++ b/accessible/android/DocAccessibleWrap.cpp
@@ -29,7 +29,7 @@ DocAccessibleWrap::DocAccessibleWrap(Document* aDocument, PresShell* aPresShell)
   nsCOMPtr<nsIDocShellTreeItem> treeItem(aDocument->GetDocShell());
 
   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
-  treeItem->GetParent(getter_AddRefs(parentTreeItem));
+  treeItem->GetInProcessParent(getter_AddRefs(parentTreeItem));
 
   if (treeItem->ItemType() == nsIDocShellTreeItem::typeContent &&
       (!parentTreeItem ||
diff --git a/accessible/base/DocManager.cpp b/accessible/base/DocManager.cpp
index 6a9035b8f843..e87e5aae23f4 100644
--- a/accessible/base/DocManager.cpp
+++ b/accessible/base/DocManager.cpp
@@ -449,7 +449,7 @@ DocAccessible* DocManager::CreateDocOrRootAccessible(Document* aDocument) {
   if (!isRootDoc) {
     // XXXaaronl: ideally we would traverse the presshell chain. Since there's
     // no easy way to do that, we cheat and use the document hierarchy.
-    parentDocAcc = GetDocAccessible(aDocument->GetParentDocument());
+    parentDocAcc = GetDocAccessible(aDocument->GetInProcessParentDocument());
     NS_ASSERTION(parentDocAcc, "Can't create an accessible for the document!");
     if (!parentDocAcc) return nullptr;
   }
diff --git a/accessible/base/Logging.cpp b/accessible/base/Logging.cpp
index 2427ffaffad5..2cb83b491359 100644
--- a/accessible/base/Logging.cpp
+++ b/accessible/base/Logging.cpp
@@ -121,7 +121,7 @@ static void LogDocShellTree(dom::Document* aDocumentNode) {
   if (aDocumentNode->IsActive()) {
     nsCOMPtr<nsIDocShellTreeItem> treeItem(aDocumentNode->GetDocShell());
     nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
-    treeItem->GetParent(getter_AddRefs(parentTreeItem));
+    treeItem->GetInProcessParent(getter_AddRefs(parentTreeItem));
     nsCOMPtr<nsIDocShellTreeItem> rootTreeItem;
     treeItem->GetRootTreeItem(getter_AddRefs(rootTreeItem));
     printf("docshell hierarchy, parent: %p, root: %p, is tab document: %s;",
@@ -182,7 +182,7 @@ static void LogDocLoadGroup(dom::Document* aDocumentNode) {
 }
 
 static void LogDocParent(dom::Document* aDocumentNode) {
-  dom::Document* parentDoc = aDocumentNode->GetParentDocument();
+  dom::Document* parentDoc = aDocumentNode->GetInProcessParentDocument();
   printf("parent DOM document: %p", static_cast<void*>(parentDoc));
   if (parentDoc) {
     printf(", parent acc document: %p",
diff --git a/accessible/base/nsAccUtils.cpp b/accessible/base/nsAccUtils.cpp
index 3ab47ea6c956..c8991b3505f7 100644
--- a/accessible/base/nsAccUtils.cpp
+++ b/accessible/base/nsAccUtils.cpp
@@ -511,12 +511,13 @@ bool nsAccUtils::IsARIALive(const Accessible* aAccessible) {
     }
 
     nsCOMPtr<nsIDocShellTreeItem> sameTypeParent;
-    docShellTreeItem->GetSameTypeParent(getter_AddRefs(sameTypeParent));
+    docShellTreeItem->GetInProcessSameTypeParent(
+        getter_AddRefs(sameTypeParent));
     if (!sameTypeParent || sameTypeParent == docShellTreeItem) {
       break;
     }
 
-    dom::Document* parentDoc = doc->GetParentDocument();
+    dom::Document* parentDoc = doc->GetInProcessParentDocument();
     if (!parentDoc) {
       break;
     }
diff --git a/accessible/base/nsCoreUtils.cpp b/accessible/base/nsCoreUtils.cpp
index 78c3650be534..a9f364674678 100644
--- a/accessible/base/nsCoreUtils.cpp
+++ b/accessible/base/nsCoreUtils.cpp
@@ -342,7 +342,7 @@ bool nsCoreUtils::IsRootDocument(Document* aDocument) {
   NS_ASSERTION(docShellTreeItem, "No document shell for document!");
 
   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
-  docShellTreeItem->GetParent(getter_AddRefs(parentTreeItem));
+  docShellTreeItem->GetInProcessParent(getter_AddRefs(parentTreeItem));
 
   return !parentTreeItem;
 }
@@ -358,7 +358,7 @@ bool nsCoreUtils::IsTabDocument(Document* aDocumentNode) {
   nsCOMPtr<nsIDocShellTreeItem> treeItem(aDocumentNode->GetDocShell());
 
   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
-  treeItem->GetParent(getter_AddRefs(parentTreeItem));
+  treeItem->GetInProcessParent(getter_AddRefs(parentTreeItem));
 
   // Tab document running in own process doesn't have parent.
   if (XRE_IsContentProcess()) return !parentTreeItem;
diff --git a/accessible/generic/Accessible.cpp b/accessible/generic/Accessible.cpp
index 696e14c088a8..2e2d34a12512 100644
--- a/accessible/generic/Accessible.cpp
+++ b/accessible/generic/Accessible.cpp
@@ -1077,10 +1077,11 @@ already_AddRefed<nsIPersistentProperties> Accessible::NativeAttributes() {
     if (!docShellTreeItem) break;
 
     nsCOMPtr<nsIDocShellTreeItem> sameTypeParent;
-    docShellTreeItem->GetSameTypeParent(getter_AddRefs(sameTypeParent));
+    docShellTreeItem->GetInProcessSameTypeParent(
+        getter_AddRefs(sameTypeParent));
     if (!sameTypeParent || sameTypeParent == docShellTreeItem) break;
 
-    dom::Document* parentDoc = doc->GetParentDocument();
+    dom::Document* parentDoc = doc->GetInProcessParentDocument();
     if (!parentDoc) break;
 
     startContent = parentDoc->FindContentForSubDocument(doc);
@@ -1788,7 +1789,7 @@ Relation Accessible::RelationByType(RelationType aType) const {
         // Walk up the parent chain without crossing the boundary at which item
         // types change, preventing us from walking up out of tab content.
         nsCOMPtr<nsIDocShellTreeItem> root;
-        docShell->GetSameTypeRootTreeItem(getter_AddRefs(root));
+        docShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
         if (root) {
           // If the item type is typeContent, we assume we are in browser tab
           // content. Note, this includes content such as about:addons,
diff --git a/accessible/generic/DocAccessible.cpp b/accessible/generic/DocAccessible.cpp
index a834e45aa428..20ff90526513 100644
--- a/accessible/generic/DocAccessible.cpp
+++ b/accessible/generic/DocAccessible.cpp
@@ -193,7 +193,7 @@ role DocAccessible::NativeRole() const {
   nsCOMPtr<nsIDocShell> docShell = nsCoreUtils::GetDocShellFor(mDocumentNode);
   if (docShell) {
     nsCOMPtr<nsIDocShellTreeItem> sameTypeRoot;
-    docShell->GetSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
+    docShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
     int32_t itemType = docShell->ItemType();
     if (sameTypeRoot == docShell) {
       // Root of content or chrome tree
@@ -498,7 +498,7 @@ nsRect DocAccessible::RelativeBounds(nsIFrame** aRelativeFrame) const {
       bounds = scrollPort;
     }
 
-    document = parentDoc = document->GetParentDocument();
+    document = parentDoc = document->GetInProcessParentDocument();
   }
 
   return bounds;
@@ -2276,7 +2276,7 @@ bool DocAccessible::IsLoadEventTarget() const {
   NS_ASSERTION(treeItem, "No document shell for document!");
 
   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
-  treeItem->GetParent(getter_AddRefs(parentTreeItem));
+  treeItem->GetInProcessParent(getter_AddRefs(parentTreeItem));
 
   // Not a root document.
   if (parentTreeItem) {
diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index 71fe7c958b5c..649d54f379d9 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -779,7 +779,7 @@ nsDocShell::LoadURI(nsDocShellLoadState* aLoadState) {
 void nsDocShell::MaybeHandleSubframeHistory(nsDocShellLoadState* aLoadState) {
   // First, verify if this is a subframe.
   nsCOMPtr<nsIDocShellTreeItem> parentAsItem;
-  GetSameTypeParent(getter_AddRefs(parentAsItem));
+  GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
   nsCOMPtr<nsIDocShell> parentDS(do_QueryInterface(parentAsItem));
 
   if (!parentDS || parentDS == static_cast<nsIDocShell*>(this)) {
@@ -1212,7 +1212,7 @@ bool nsDocShell::SetCurrentURI(nsIURI* aURI, nsIRequest* aRequest,
 
   nsCOMPtr<nsIDocShellTreeItem> root;
 
-  GetSameTypeRootTreeItem(getter_AddRefs(root));
+  GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   if (root.get() == static_cast<nsIDocShellTreeItem*>(this)) {
     // This is the root docshell
     isRoot = true;
@@ -1852,7 +1852,7 @@ nsDocShell::GetFullscreenAllowed(bool* aFullscreenAllowed) {
   // If we have no parent then we're the root docshell; no ancestor of the
   // original docshell doesn't have a allowfullscreen attribute, so
   // report fullscreen as allowed.
-  RefPtr<nsDocShell> parent = GetParentDocshell();
+  RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
   if (!parent) {
     *aFullscreenAllowed = true;
     return NS_OK;
@@ -2215,7 +2215,7 @@ nsresult nsDocShell::Now(DOMHighResTimeStamp* aWhen) {
 
 NS_IMETHODIMP
 nsDocShell::SetWindowDraggingAllowed(bool aValue) {
-  RefPtr<nsDocShell> parent = GetParentDocshell();
+  RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
   if (!aValue && mItemType == typeChrome && !parent) {
     // Window dragging is always allowed for top level
     // chrome docshells.
@@ -2230,7 +2230,7 @@ nsDocShell::GetWindowDraggingAllowed(bool* aValue) {
   // window dragging regions in CSS (-moz-window-drag:drag)
   // can be slow. Default behavior is to only allow it for
   // chrome top level windows.
-  RefPtr<nsDocShell> parent = GetParentDocshell();
+  RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
   if (mItemType == typeChrome && !parent) {
     // Top level chrome window
     *aValue = true;
@@ -2244,7 +2244,7 @@ nsIDOMStorageManager* nsDocShell::TopSessionStorageManager() {
   nsresult rv;
 
   nsCOMPtr<nsIDocShellTreeItem> topItem;
-  rv = GetSameTypeRootTreeItem(getter_AddRefs(topItem));
+  rv = GetInProcessSameTypeRootTreeItem(getter_AddRefs(topItem));
   if (NS_FAILED(rv)) {
     return nullptr;
   }
@@ -2462,7 +2462,7 @@ nsDocShell::GetItemType(int32_t* aItemType) {
 }
 
 NS_IMETHODIMP
-nsDocShell::GetParent(nsIDocShellTreeItem** aParent) {
+nsDocShell::GetInProcessParent(nsIDocShellTreeItem** aParent) {
   if (!mParent) {
     *aParent = nullptr;
   } else {
@@ -2473,7 +2473,14 @@ nsDocShell::GetParent(nsIDocShellTreeItem** aParent) {
   return NS_OK;
 }
 
-already_AddRefed<nsDocShell> nsDocShell::GetParentDocshell() {
+// With Fission, related nsDocShell objects may exist in a different process. In
+// that case, this method will return `nullptr`, despite a parent nsDocShell
+// object existing.
+//
+// Prefer using `BrowsingContext::Parent()`, which will succeed even if the
+// parent entry is not in the current process, and handle the case where the
+// parent nsDocShell is inaccessible.
+already_AddRefed<nsDocShell> nsDocShell::GetInProcessParentDocshell() {
   nsCOMPtr<nsIDocShell> docshell = do_QueryInterface(GetAsSupports(mParent));
   return docshell.forget().downcast<nsDocShell>();
 }
@@ -2534,7 +2541,7 @@ void nsDocShell::MaybeCreateInitialClientSource(nsIPrincipal* aPrincipal) {
   mInitialClientSource->DocShellExecutionReady(this);
 
   // Next, check to see if the parent is controlled.
-  nsCOMPtr<nsIDocShell> parent = GetParentDocshell();
+  nsCOMPtr<nsIDocShell> parent = GetInProcessParentDocshell();
   nsPIDOMWindowOuter* parentOuter = parent ? parent->GetWindow() : nullptr;
   nsPIDOMWindowInner* parentInner =
       parentOuter ? parentOuter->GetCurrentInnerWindow() : nullptr;
@@ -2577,7 +2584,7 @@ Maybe<ClientInfo> nsDocShell::GetInitialClientInfo() const {
 
 void nsDocShell::RecomputeCanExecuteScripts() {
   bool old = mCanExecuteScripts;
-  RefPtr<nsDocShell> parent = GetParentDocshell();
+  RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
 
   // If we have no tree owner, that means that we've been detached from the
   // docshell tree (this is distinct from having no parent docshell, which
@@ -2741,7 +2748,7 @@ void nsDocShell::MaybeClearStorageAccessFlag() {
 }
 
 NS_IMETHODIMP
-nsDocShell::GetSameTypeParent(nsIDocShellTreeItem** aParent) {
+nsDocShell::GetInProcessSameTypeParent(nsIDocShellTreeItem** aParent) {
   NS_ENSURE_ARG_POINTER(aParent);
   *aParent = nullptr;
 
@@ -2784,10 +2791,10 @@ nsDocShell::GetRootTreeItem(nsIDocShellTreeItem** aRootTreeItem) {
   NS_ENSURE_ARG_POINTER(aRootTreeItem);
 
   RefPtr<nsDocShell> root = this;
-  RefPtr<nsDocShell> parent = root->GetParentDocshell();
+  RefPtr<nsDocShell> parent = root->GetInProcessParentDocshell();
   while (parent) {
     root = parent;
-    parent = root->GetParentDocshell();
+    parent = root->GetInProcessParentDocshell();
   }
 
   root.forget(aRootTreeItem);
@@ -2795,17 +2802,18 @@ nsDocShell::GetRootTreeItem(nsIDocShellTreeItem** aRootTreeItem) {
 }
 
 NS_IMETHODIMP
-nsDocShell::GetSameTypeRootTreeItem(nsIDocShellTreeItem** aRootTreeItem) {
+nsDocShell::GetInProcessSameTypeRootTreeItem(
+    nsIDocShellTreeItem** aRootTreeItem) {
   NS_ENSURE_ARG_POINTER(aRootTreeItem);
   *aRootTreeItem = static_cast<nsIDocShellTreeItem*>(this);
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  NS_ENSURE_SUCCESS(GetSameTypeParent(getter_AddRefs(parent)),
+  NS_ENSURE_SUCCESS(GetInProcessSameTypeParent(getter_AddRefs(parent)),
                     NS_ERROR_FAILURE);
   while (parent) {
     *aRootTreeItem = parent;
     NS_ENSURE_SUCCESS(
-        (*aRootTreeItem)->GetSameTypeParent(getter_AddRefs(parent)),
+        (*aRootTreeItem)->GetInProcessSameTypeParent(getter_AddRefs(parent)),
         NS_ERROR_FAILURE);
   }
   NS_ADDREF(*aRootTreeItem);
@@ -2884,11 +2892,12 @@ bool nsDocShell::CanAccessItem(nsIDocShellTreeItem* aTargetItem,
   }
 
   nsCOMPtr<nsIDocShellTreeItem> accessingRoot;
-  aAccessingItem->GetSameTypeRootTreeItem(getter_AddRefs(accessingRoot));
+  aAccessingItem->GetInProcessSameTypeRootTreeItem(
+      getter_AddRefs(accessingRoot));
   nsCOMPtr<nsIDocShell> accessingRootDS = do_QueryInterface(accessingRoot);
 
   nsCOMPtr<nsIDocShellTreeItem> targetRoot;
-  aTargetItem->GetSameTypeRootTreeItem(getter_AddRefs(targetRoot));
+  aTargetItem->GetInProcessSameTypeRootTreeItem(getter_AddRefs(targetRoot));
   nsCOMPtr<nsIDocShell> targetRootDS = do_QueryInterface(targetRoot);
 
   OriginAttributes targetOA =
@@ -2950,7 +2959,7 @@ bool nsDocShell::CanAccessItem(nsIDocShellTreeItem* aTargetItem,
     }
 
     nsCOMPtr<nsIDocShellTreeItem> parent;
-    target->GetSameTypeParent(getter_AddRefs(parent));
+    target->GetInProcessSameTypeParent(getter_AddRefs(parent));
     parent.swap(target);
   } while (target);
 
@@ -3027,12 +3036,12 @@ nsDocShell::FindItemWithName(const nsAString& aName,
       // a blank name himself.
       return NS_OK;
     } else if (aName.LowerCaseEqualsLiteral("_parent")) {
-      GetSameTypeParent(getter_AddRefs(foundItem));
+      GetInProcessSameTypeParent(getter_AddRefs(foundItem));
       if (!foundItem) {
         foundItem = this;
       }
     } else if (aName.LowerCaseEqualsLiteral("_top")) {
-      GetSameTypeRootTreeItem(getter_AddRefs(foundItem));
+      GetInProcessSameTypeRootTreeItem(getter_AddRefs(foundItem));
       NS_ASSERTION(foundItem, "Must have this; worst case it's us!");
     } else {
       // Do the search for item by an actual name.
@@ -3103,8 +3112,8 @@ nsresult nsDocShell::DoFindItemWithName(const nsAString& aName,
     }
 
     // If we have a same-type parent, respecting browser and app boundaries.
-    // NOTE: Could use GetSameTypeParent if the issues described in bug 1310344
-    // are fixed.
+    // NOTE: Could use GetInProcessSameTypeParent if the issues described in
+    // bug 1310344 are fixed.
     if (!GetIsMozBrowser() && parentAsTreeItem->ItemType() == mItemType) {
       return parentAsTreeItem->FindItemWithName(aName, this, aOriginalRequestor,
                                                 /* aSkipTabGroup = */ false,
@@ -3151,7 +3160,7 @@ bool nsDocShell::IsSandboxedFrom(nsIDocShell* aTargetDocShell) {
 
   // If aTargetDocShell has an ancestor, it is not top level.
   nsCOMPtr<nsIDocShellTreeItem> ancestorOfTarget;
-  aTargetDocShell->GetSameTypeParent(getter_AddRefs(ancestorOfTarget));
+  aTargetDocShell->GetInProcessSameTypeParent(getter_AddRefs(ancestorOfTarget));
   if (ancestorOfTarget) {
     do {
       // We are not sandboxed if we are an ancestor of target.
@@ -3159,7 +3168,8 @@ bool nsDocShell::IsSandboxedFrom(nsIDocShell* aTargetDocShell) {
         return false;
       }
       nsCOMPtr<nsIDocShellTreeItem> tempTreeItem;
-      ancestorOfTarget->GetSameTypeParent(getter_AddRefs(tempTreeItem));
+      ancestorOfTarget->GetInProcessSameTypeParent(
+          getter_AddRefs(tempTreeItem));
       tempTreeItem.swap(ancestorOfTarget);
     } while (ancestorOfTarget);
 
@@ -3180,7 +3190,7 @@ bool nsDocShell::IsSandboxedFrom(nsIDocShell* aTargetDocShell) {
   // from our top.
   if (!(sandboxFlags & SANDBOXED_TOPLEVEL_NAVIGATION)) {
     nsCOMPtr<nsIDocShellTreeItem> rootTreeItem;
-    GetSameTypeRootTreeItem(getter_AddRefs(rootTreeItem));
+    GetInProcessSameTypeRootTreeItem(getter_AddRefs(rootTreeItem));
     if (SameCOMIdentity(aTargetDocShell, rootTreeItem)) {
       return false;
     }
@@ -3292,7 +3302,7 @@ nsDocShell::GetIsInUnload(bool* aIsInUnload) {
 }
 
 NS_IMETHODIMP
-nsDocShell::GetChildCount(int32_t* aChildCount) {
+nsDocShell::GetInProcessChildCount(int32_t* aChildCount) {
   NS_ENSURE_ARG_POINTER(aChildCount);
   *aChildCount = mChildList.Length();
   return NS_OK;
@@ -3414,7 +3424,7 @@ nsDocShell::RemoveChild(nsIDocShellTreeItem* aChild) {
 }
 
 NS_IMETHODIMP
-nsDocShell::GetChildAt(int32_t aIndex, nsIDocShellTreeItem** aChild) {
+nsDocShell::GetInProcessChildAt(int32_t aIndex, nsIDocShellTreeItem** aChild) {
   NS_ENSURE_ARG_POINTER(aChild);
 
 #ifdef DEBUG
@@ -3664,7 +3674,7 @@ nsDocShell::GetUseGlobalHistory(bool* aUseGlobalHistory) {
 NS_IMETHODIMP
 nsDocShell::RemoveFromSessionHistory() {
   nsCOMPtr<nsIDocShellTreeItem> root;
-  GetSameTypeRootTreeItem(getter_AddRefs(root));
+  GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   nsCOMPtr<nsIWebNavigation> rootAsWebnav = do_QueryInterface(root);
   if (!rootAsWebnav) {
     return NS_OK;
@@ -4814,7 +4824,7 @@ nsDocShell::InitSessionHistory() {
   // Make sure that we are the root DocShell, and set a handle to root docshell
   // in the session history.
   nsCOMPtr<nsIDocShellTreeItem> root;
-  GetSameTypeRootTreeItem(getter_AddRefs(root));
+  GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   if (root != this) {
     return NS_ERROR_FAILURE;
   }
@@ -5327,7 +5337,7 @@ nsDocShell::GetVisibility(bool* aVisibility) {
   // would make this test meaningless.
 
   RefPtr<nsDocShell> docShell = this;
-  RefPtr<nsDocShell> parentItem = docShell->GetParentDocshell();
+  RefPtr<nsDocShell> parentItem = docShell->GetInProcessParentDocshell();
   while (parentItem) {
     // Null-check for crash in bug 267804
     if (!parentItem->GetPresShell()) {
@@ -5358,7 +5368,7 @@ nsDocShell::GetVisibility(bool* aVisibility) {
     }
 
     docShell = parentItem;
-    parentItem = docShell->GetParentDocshell();
+    parentItem = docShell->GetInProcessParentDocshell();
   }
 
   nsCOMPtr<nsIBaseWindow> treeOwnerAsWin(do_QueryInterface(mTreeOwner));
@@ -5406,7 +5416,7 @@ nsDocShell::SetIsActive(bool aIsActive) {
       // Update orientation when the top-level browsing context becomes active.
       if (aIsActive) {
         nsCOMPtr<nsIDocShellTreeItem> parent;
-        GetSameTypeParent(getter_AddRefs(parent));
+        GetInProcessSameTypeParent(getter_AddRefs(parent));
         if (!parent) {
           // We only care about the top-level browsing context.
           uint16_t orientation = OrientationLock();
@@ -5556,7 +5566,7 @@ nsDocShell::SetMixedContentChannel(nsIChannel* aMixedContentChannel) {
   if (aMixedContentChannel) {
     // Get the root docshell.
     nsCOMPtr<nsIDocShellTreeItem> root;
-    GetSameTypeRootTreeItem(getter_AddRefs(root));
+    GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
     NS_WARNING_ASSERTION(root.get() == static_cast<nsIDocShellTreeItem*>(this),
                          "Setting mMixedContentChannel on a docshell that is "
                          "not the root docshell");
@@ -5594,7 +5604,7 @@ nsDocShell::GetAllowMixedContentAndConnectionData(
   *aIsRootDocShell = false;
 
   nsCOMPtr<nsIDocShellTreeItem> sameTypeRoot;
-  GetSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
+  GetInProcessSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
   NS_ASSERTION(
       sameTypeRoot,
       "No document shell root tree item from document shell tree item!");
@@ -5681,7 +5691,7 @@ nsDocShell::SetTitle(const nsAString& aTitle) {
   mTitleValidForCurrentURI = true;
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  GetSameTypeParent(getter_AddRefs(parent));
+  GetInProcessSameTypeParent(getter_AddRefs(parent));
 
   // When title is set on the top object it should then be passed to the
   // tree owner.
@@ -6730,7 +6740,7 @@ nsresult nsDocShell::EndPageLoad(nsIWebProgress* aProgress,
   // Test whether this is the top frame or a subframe
   bool isTopFrame = true;
   nsCOMPtr<nsIDocShellTreeItem> targetParentTreeItem;
-  rv = GetSameTypeParent(getter_AddRefs(targetParentTreeItem));
+  rv = GetInProcessSameTypeParent(getter_AddRefs(targetParentTreeItem));
   if (NS_SUCCEEDED(rv) && targetParentTreeItem) {
     isTopFrame = false;
   }
@@ -6774,7 +6784,7 @@ nsresult nsDocShell::EndPageLoad(nsIWebProgress* aProgress,
 
       // Parent window
       nsCOMPtr<nsIDocShellTreeItem> parentItem;
-      GetSameTypeParent(getter_AddRefs(parentItem));
+      GetInProcessSameTypeParent(getter_AddRefs(parentItem));
       if (!parentItem) {
         return NS_OK;
       }
@@ -7015,7 +7025,7 @@ nsresult nsDocShell::EnsureContentViewer() {
   nsIPrincipal* principal = GetInheritedPrincipal(false);
   nsIPrincipal* storagePrincipal = GetInheritedPrincipal(false, true);
   nsCOMPtr<nsIDocShellTreeItem> parentItem;
-  GetSameTypeParent(getter_AddRefs(parentItem));
+  GetInProcessSameTypeParent(getter_AddRefs(parentItem));
   if (parentItem) {
     if (nsCOMPtr<nsPIDOMWindowOuter> domWin = GetWindow()) {
       nsCOMPtr<Element> parentElement = domWin->GetFrameElementInternal();
@@ -7266,7 +7276,7 @@ bool nsDocShell::CanSavePresentation(uint32_t aLoadType,
 
   // Don't cache the content viewer if we're in a subframe.
   nsCOMPtr<nsIDocShellTreeItem> root;
-  GetSameTypeParent(getter_AddRefs(root));
+  GetInProcessSameTypeParent(getter_AddRefs(root));
   if (root && root != this) {
     return false;  // this is a subframe load
   }
@@ -7902,7 +7912,7 @@ nsresult nsDocShell::RestoreFromHistory() {
   }
 
   if (document) {
-    RefPtr<nsDocShell> parent = GetParentDocshell();
+    RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
     if (parent) {
       RefPtr<Document> d = parent->GetDocument();
       if (d) {
@@ -8314,7 +8324,7 @@ nsresult nsDocShell::CreateContentViewer(const nsACString& aContentType,
 
       RefPtr<Document> newDoc = viewer->GetDocument();
 
-      RefPtr<nsDocShell> parent = GetParentDocshell();
+      RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
       nsCOMPtr<nsIPrincipal> parentPrincipal =
           parent->GetDocument()->NodePrincipal();
       nsCOMPtr<nsIPrincipal> thisPrincipal = newDoc->NodePrincipal();
@@ -8445,7 +8455,7 @@ nsresult nsDocShell::SetupNewViewer(nsIContentViewer* aNewViewer) {
   DoGetPositionAndSize(&x, &y, &cx, &cy);
 
   nsCOMPtr<nsIDocShellTreeItem> parentAsItem;
-  NS_ENSURE_SUCCESS(GetSameTypeParent(getter_AddRefs(parentAsItem)),
+  NS_ENSURE_SUCCESS(GetInProcessSameTypeParent(getter_AddRefs(parentAsItem)),
                     NS_ERROR_FAILURE);
   nsCOMPtr<nsIDocShell> parent(do_QueryInterface(parentAsItem));
 
@@ -8642,7 +8652,7 @@ nsresult nsDocShell::CheckLoadingPermissions() {
     }
 
     nsCOMPtr<nsIDocShellTreeItem> tmp;
-    item->GetSameTypeParent(getter_AddRefs(tmp));
+    item->GetInProcessSameTypeParent(getter_AddRefs(tmp));
     item.swap(tmp);
   } while (item);
 
@@ -9440,7 +9450,7 @@ nsresult nsDocShell::InternalLoad(nsDocShellLoadState* aLoadState,
 
   // If this docshell is owned by a frameloader, make sure to cancel
   // possible frameloader initialization before loading a new page.
-  nsCOMPtr<nsIDocShellTreeItem> parent = GetParentDocshell();
+  nsCOMPtr<nsIDocShellTreeItem> parent = GetInProcessParentDocshell();
   if (parent) {
     RefPtr<Document> doc = parent->GetDocument();
     if (doc) {
@@ -9628,7 +9638,7 @@ nsresult nsDocShell::InternalLoad(nsDocShellLoadState* aLoadState,
   if (OrientationLock() != hal::eScreenOrientation_None) {
 #ifdef DEBUG
     nsCOMPtr<nsIDocShellTreeItem> parent;
-    GetSameTypeParent(getter_AddRefs(parent));
+    GetInProcessSameTypeParent(getter_AddRefs(parent));
     MOZ_ASSERT(!parent);
 #endif
     SetOrientationLock(hal::eScreenOrientation_None);
@@ -9781,7 +9791,7 @@ nsIPrincipal* nsDocShell::GetInheritedPrincipal(
 
   if (!document) {
     nsCOMPtr<nsIDocShellTreeItem> parentItem;
-    GetSameTypeParent(getter_AddRefs(parentItem));
+    GetInProcessSameTypeParent(getter_AddRefs(parentItem));
     if (parentItem) {
       document = parentItem->GetDocument();
     }
@@ -11575,7 +11585,7 @@ nsresult nsDocShell::AddToSessionHistory(
 
   // Get a handle to the root docshell
   nsCOMPtr<nsIDocShellTreeItem> root;
-  GetSameTypeRootTreeItem(getter_AddRefs(root));
+  GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   /*
    * If this is a LOAD_FLAGS_REPLACE_HISTORY in a subframe, we use
    * the existing SH entry in the page and replace the url and
@@ -11969,7 +11979,7 @@ void nsDocShell::SetHistoryEntry(nsCOMPtr<nsISHEntry>* aPtr,
     nsCOMPtr<nsISHEntry> oldRootEntry = nsSHistory::GetRootSHEntry(*aPtr);
     if (oldRootEntry) {
       nsCOMPtr<nsIDocShellTreeItem> rootAsItem;
-      GetSameTypeRootTreeItem(getter_AddRefs(rootAsItem));
+      GetInProcessSameTypeRootTreeItem(getter_AddRefs(rootAsItem));
       nsCOMPtr<nsIDocShell> rootShell = do_QueryInterface(rootAsItem);
       if (rootShell) {  // if we're the root just set it, nothing to swap
         nsSHistory::SwapEntriesData data = {this, newRootEntry};
@@ -11991,7 +12001,7 @@ void nsDocShell::SetHistoryEntry(nsCOMPtr<nsISHEntry>* aPtr,
 
 already_AddRefed<ChildSHistory> nsDocShell::GetRootSessionHistory() {
   nsCOMPtr<nsIDocShellTreeItem> root;
-  nsresult rv = GetSameTypeRootTreeItem(getter_AddRefs(root));
+  nsresult rv = GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return nullptr;
   }
@@ -12503,7 +12513,7 @@ NS_IMETHODIMP
 nsDocShell::GetTopWindow(mozIDOMWindowProxy** aWindow) {
   nsCOMPtr<nsPIDOMWindowOuter> win = GetWindow();
   if (win) {
-    win = win->GetTop();
+    win = win->GetInProcessTop();
   }
   win.forget(aWindow);
   return NS_OK;
@@ -12517,7 +12527,7 @@ nsDocShell::GetTopFrameElement(Element** aElement) {
     return NS_OK;
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> top = win->GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> top = win->GetInProcessScriptableTop();
   NS_ENSURE_TRUE(top, NS_ERROR_FAILURE);
 
   // GetFrameElementInternal, /not/ GetScriptableFrameElement -- if |top| is
@@ -12546,7 +12556,7 @@ nsDocShell::GetUseTrackingProtection(bool* aUseTrackingProtection) {
     return NS_OK;
   }
 
-  RefPtr<nsDocShell> parent = GetParentDocshell();
+  RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
   if (parent) {
     return parent->GetUseTrackingProtection(aUseTrackingProtection);
   }
@@ -13175,7 +13185,7 @@ uint32_t nsDocShell::GetInheritedFrameType() {
   }
 
   nsCOMPtr<nsIDocShellTreeItem> parentAsItem;
-  GetSameTypeParent(getter_AddRefs(parentAsItem));
+  GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
 
   nsCOMPtr<nsIDocShell> parent = do_QueryInterface(parentAsItem);
   if (!parent) {
@@ -13219,7 +13229,7 @@ NS_IMETHODIMP nsDocShell::GetIsTopLevelContentDocShell(
 
   if (mItemType == typeContent) {
     nsCOMPtr<nsIDocShellTreeItem> root;
-    GetSameTypeRootTreeItem(getter_AddRefs(root));
+    GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
     *aIsTopLevelContentDocShell =
         root.get() == static_cast<nsIDocShellTreeItem*>(this);
   }
@@ -13279,7 +13289,7 @@ bool nsDocShell::ServiceWorkerAllowedToControlWindow(nsIPrincipal* aPrincipal,
   }
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  GetSameTypeParent(getter_AddRefs(parent));
+  GetInProcessSameTypeParent(getter_AddRefs(parent));
   nsPIDOMWindowOuter* parentOuter = parent ? parent->GetWindow() : nullptr;
   nsPIDOMWindowInner* parentInner =
       parentOuter ? parentOuter->GetCurrentInnerWindow() : nullptr;
@@ -13403,14 +13413,14 @@ nsDocShell::GetAsyncPanZoomEnabled(bool* aOut) {
 }
 
 bool nsDocShell::HasUnloadedParent() {
-  RefPtr<nsDocShell> parent = GetParentDocshell();
+  RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
   while (parent) {
     bool inUnload = false;
     parent->GetIsInUnload(&inUnload);
     if (inUnload) {
       return true;
     }
-    parent = parent->GetParentDocshell();
+    parent = parent->GetInProcessParentDocshell();
   }
   return false;
 }
@@ -13519,7 +13529,7 @@ bool nsDocShell::InFrameSwap() {
     if (shell->mInFrameSwap) {
       return true;
     }
-    shell = shell->GetParentDocshell();
+    shell = shell->GetInProcessParentDocshell();
   } while (shell);
   return false;
 }
@@ -13574,7 +13584,7 @@ nsDocShell::GetIsOnlyToplevelInTabGroup(bool* aResult) {
 
   // If we are not toplevel then we are not the only toplevel window in the
   // tab group.
-  if (outer->GetScriptableParentOrNull()) {
+  if (outer->GetInProcessScriptableParentOrNull()) {
     *aResult = false;
     return NS_OK;
   }
diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
index f8414d05e017..44ffc3937736 100644
--- a/docshell/base/nsDocShell.h
+++ b/docshell/base/nsDocShell.h
@@ -328,7 +328,7 @@ class nsDocShell final : public nsDocLoader,
   // background loading, it triggers the parent docshell to see if the parent
   // document can fire load event earlier.
   void TriggerParentCheckDocShellIsEmpty() {
-    RefPtr<nsDocShell> parent = GetParentDocshell();
+    RefPtr<nsDocShell> parent = GetInProcessParentDocshell();
     if (parent) {
       parent->DocLoaderIsEmpty(true);
     }
@@ -934,7 +934,7 @@ class nsDocShell final : public nsDocLoader,
                               nsIDocShellTreeItem** aResult);
 
   // Convenience method for getting our parent docshell. Can return null
-  already_AddRefed<nsDocShell> GetParentDocshell();
+  already_AddRefed<nsDocShell> GetInProcessParentDocshell();
 
   // Helper assertion to enforce that mInPrivateBrowsing is in sync with
   // OriginAttributes.mPrivateBrowsingId
diff --git a/docshell/base/nsDocShellEnumerator.cpp b/docshell/base/nsDocShellEnumerator.cpp
index a1404594f474..ecb747be860c 100644
--- a/docshell/base/nsDocShellEnumerator.cpp
+++ b/docshell/base/nsDocShellEnumerator.cpp
@@ -122,14 +122,14 @@ nsresult nsDocShellForwardsEnumerator::BuildArrayRecursive(
   }
 
   int32_t numChildren;
-  rv = aItem->GetChildCount(&numChildren);
+  rv = aItem->GetInProcessChildCount(&numChildren);
   if (NS_FAILED(rv)) {
     return rv;
   }
 
   for (int32_t i = 0; i < numChildren; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> curChild;
-    rv = aItem->GetChildAt(i, getter_AddRefs(curChild));
+    rv = aItem->GetInProcessChildAt(i, getter_AddRefs(curChild));
     if (NS_FAILED(rv)) {
       return rv;
     }
@@ -148,14 +148,14 @@ nsresult nsDocShellBackwardsEnumerator::BuildArrayRecursive(
   nsresult rv;
 
   int32_t numChildren;
-  rv = aItem->GetChildCount(&numChildren);
+  rv = aItem->GetInProcessChildCount(&numChildren);
   if (NS_FAILED(rv)) {
     return rv;
   }
 
   for (int32_t i = numChildren - 1; i >= 0; --i) {
     nsCOMPtr<nsIDocShellTreeItem> curChild;
-    rv = aItem->GetChildAt(i, getter_AddRefs(curChild));
+    rv = aItem->GetInProcessChildAt(i, getter_AddRefs(curChild));
     if (NS_FAILED(rv)) {
       return rv;
     }
diff --git a/docshell/base/nsDocShellTreeOwner.cpp b/docshell/base/nsDocShellTreeOwner.cpp
index 602565d84770..62f3c081f346 100644
--- a/docshell/base/nsDocShellTreeOwner.cpp
+++ b/docshell/base/nsDocShellTreeOwner.cpp
@@ -1223,7 +1223,7 @@ bool ChromeTooltipListener::WebProgressShowedTooltip(
     // alive here. So we use the document hierarchy instead:
     Document* document = lastUsed->GetDocument();
     if (document) {
-      document = document->GetParentDocument();
+      document = document->GetInProcessParentDocument();
     }
     if (!document) {
       break;
diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
index 507980e65e42..3f44233fd7ca 100644
--- a/docshell/base/nsIDocShell.idl
+++ b/docshell/base/nsIDocShell.idl
@@ -779,12 +779,16 @@ interface nsIDocShell : nsIDocShellTreeItem
   /**
    * Like nsIDocShellTreeItem::GetSameTypeParent, except this ignores <iframe
    * mozbrowser> boundaries.
+   *
+   * @deprecated: Use `BrowsingContext::GetParent()` in the future.
    */
   nsIDocShell getSameTypeParentIgnoreBrowserBoundaries();
 
   /**
    * Like nsIDocShellTreeItem::GetSameTypeRootTreeItem, except this ignores
    * <iframe mozbrowser> boundaries.
+   *
+   * @deprecated: Use `BrowsingContext::Top()` in the future.
    */
   nsIDocShell getSameTypeRootTreeItemIgnoreBrowserBoundaries();
 
diff --git a/docshell/base/nsIDocShellTreeItem.idl b/docshell/base/nsIDocShellTreeItem.idl
index a98239057a18..2a277ae1290d 100644
--- a/docshell/base/nsIDocShellTreeItem.idl
+++ b/docshell/base/nsIDocShellTreeItem.idl
@@ -11,6 +11,7 @@ interface nsIDocShellTreeOwner;
 interface nsPIDOMWindowOuter;
 
 webidl Document;
+webidl BrowsingContext;
 
 /**
  * The nsIDocShellTreeItem supplies the methods that are required of any item
@@ -53,7 +54,11 @@ interface nsIDocShellTreeItem : nsISupports
 
 	/*
 	Parent DocShell.
+
+	@deprecated: Use `BrowsingContext::GetParent()` instead.
+	(NOTE: `BrowsingContext::GetParent()` will not cross isolation boundaries)
 	*/
+	[binaryname(InProcessParent)]
 	readonly attribute nsIDocShellTreeItem parent;
 
 	/*
@@ -61,12 +66,18 @@ interface nsIDocShellTreeItem : nsISupports
 	is of a different itemType, or if the parent is an <iframe mozbrowser>.
 	It will instead return nullptr.  This call is a convience function for
 	Ithose wishing to not cross the boundaries at which item types change.
+
+	@deprecated: Use `BrowsingContext::GetParent()` instead.
 	*/
+	[binaryname(InProcessSameTypeParent)]
 	readonly attribute nsIDocShellTreeItem sameTypeParent;
 
 	/*
 	Returns the root DocShellTreeItem.  This is a convience equivalent to
 	getting the parent and its parent until there isn't a parent.
+
+	@deprecated: Use `BrowsingContext::Top()` instead.
+	(NOTE: `BrowsingContext::Top()` will not cross isolation boundaries)
 	*/
 	readonly attribute nsIDocShellTreeItem rootTreeItem;
 
@@ -74,7 +85,10 @@ interface nsIDocShellTreeItem : nsISupports
 	Returns the root DocShellTreeItem of the same type.  This is a convience
 	equivalent to getting the parent of the same type and its parent until
 	there isn't a parent.
+
+	@deprecated: Use `BrowsingContext::Top()` instead.
 	*/
+	[binaryname(InProcessSameTypeRootTreeItem)]
 	readonly attribute nsIDocShellTreeItem sameTypeRootTreeItem;
 
 	/*
@@ -134,30 +148,41 @@ interface nsIDocShellTreeItem : nsISupports
 	/*
 	The current number of DocShells which are immediate children of the
 	this object.
+
+
+	@deprecated: Prefer using `BrowsingContext::Children()`, as this count will
+	not include out-of-process iframes.
 	*/
+	[binaryname(InProcessChildCount)]
 	readonly attribute long childCount;
 
 	/*
 	Add a new child DocShellTreeItem.  Adds to the end of the list.
 	Note that this does NOT take a reference to the child.  The child stays
 	alive only as long as it's referenced from outside the docshell tree.
+
 	@throws NS_ERROR_ILLEGAL_VALUE if child corresponds to the same
 	        object as this treenode or an ancestor of this treenode
 	@throws NS_ERROR_UNEXPECTED if this node is a leaf in the tree.
 	*/
-	void addChild(in nsIDocShellTreeItem child);
+	[noscript] void addChild(in nsIDocShellTreeItem child);
 
 	/*
 	Removes a child DocShellTreeItem.
+
 	@throws NS_ERROR_UNEXPECTED if this node is a leaf in the tree.
 	*/
-	void removeChild(in nsIDocShellTreeItem child);
+	[noscript] void removeChild(in nsIDocShellTreeItem child);
 
 	/**
 	 * Return the child at the index requested.  This is 0-based.
 	 *
+	 * @deprecated: Prefer using `BrowsingContext::Children()`, as this will not
+	 * include out-of-process iframes.
+	 *
 	 * @throws NS_ERROR_UNEXPECTED if the index is out of range
 	 */
+	[binaryname(GetInProcessChildAt)]
 	nsIDocShellTreeItem getChildAt(in long index);
 
 	/*
diff --git a/docshell/shistory/nsSHistory.cpp b/docshell/shistory/nsSHistory.cpp
index 2ac449ad99b4..c42f27824969 100644
--- a/docshell/shistory/nsSHistory.cpp
+++ b/docshell/shistory/nsSHistory.cpp
@@ -385,10 +385,10 @@ nsresult nsSHistory::WalkHistoryEntries(nsISHEntry* aRootEntry,
       // Walk the children of aRootShell and see if one of them
       // has srcChild as a SHEntry.
       int32_t length;
-      aRootShell->GetChildCount(&length);
+      aRootShell->GetInProcessChildCount(&length);
       for (int32_t i = 0; i < length; i++) {
         nsCOMPtr<nsIDocShellTreeItem> item;
-        nsresult rv = aRootShell->GetChildAt(i, getter_AddRefs(item));
+        nsresult rv = aRootShell->GetInProcessChildAt(i, getter_AddRefs(item));
         NS_ENSURE_SUCCESS(rv, rv);
         nsDocShell* child = static_cast<nsDocShell*>(item.get());
         if (child->HasHistoryEntry(childEntry)) {
@@ -1391,13 +1391,13 @@ nsresult nsSHistory::LoadDifferingEntries(nsISHEntry* aPrevEntry,
   int32_t pcnt = aPrevEntry->GetChildCount();
   int32_t ncnt = aNextEntry->GetChildCount();
   int32_t dsCount = 0;
-  aParent->GetChildCount(&dsCount);
+  aParent->GetInProcessChildCount(&dsCount);
 
   // Create an array for child docshells.
   nsCOMArray<nsIDocShell> docshells;
   for (int32_t i = 0; i < dsCount; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> treeItem;
-    aParent->GetChildAt(i, getter_AddRefs(treeItem));
+    aParent->GetInProcessChildAt(i, getter_AddRefs(treeItem));
     nsCOMPtr<nsIDocShell> shell = do_QueryInterface(treeItem);
     if (shell) {
       docshells.AppendElement(shell.forget());
diff --git a/dom/audiochannel/AudioChannelAgent.cpp b/dom/audiochannel/AudioChannelAgent.cpp
index 3acb79f350ae..bf2ebfc193b0 100644
--- a/dom/audiochannel/AudioChannelAgent.cpp
+++ b/dom/audiochannel/AudioChannelAgent.cpp
@@ -64,7 +64,7 @@ AudioChannelAgent::InitWithWeakCallback(
 }
 
 nsresult AudioChannelAgent::FindCorrectWindow(nsPIDOMWindowInner* aWindow) {
-  mWindow = aWindow->GetScriptableTop();
+  mWindow = aWindow->GetInProcessScriptableTop();
   if (NS_WARN_IF(!mWindow)) {
     return NS_OK;
   }
@@ -76,7 +76,7 @@ nsresult AudioChannelAgent::FindCorrectWindow(nsPIDOMWindowInner* aWindow) {
   // iframe (what is controlled by the system app).
   // For doing this we go recursively back into the chain of windows until we
   // find apps that are not the system one.
-  nsCOMPtr<nsPIDOMWindowOuter> outerParent = mWindow->GetParent();
+  nsCOMPtr<nsPIDOMWindowOuter> outerParent = mWindow->GetInProcessParent();
   if (!outerParent || outerParent == mWindow) {
     return NS_OK;
   }
diff --git a/dom/audiochannel/AudioChannelService.cpp b/dom/audiochannel/AudioChannelService.cpp
index 1c2a5e46e02a..e1b00837efff 100644
--- a/dom/audiochannel/AudioChannelService.cpp
+++ b/dom/audiochannel/AudioChannelService.cpp
@@ -346,7 +346,8 @@ AudioPlaybackConfig AudioChannelService::GetMediaConfig(
       config.mSuspend = window->GetMediaSuspend();
     }
 
-    nsCOMPtr<nsPIDOMWindowOuter> win = window->GetScriptableParentOrNull();
+    nsCOMPtr<nsPIDOMWindowOuter> win =
+        window->GetInProcessScriptableParentOrNull();
     if (!win) {
       break;
     }
@@ -419,7 +420,7 @@ void AudioChannelService::RefreshAgents(
     const std::function<void(AudioChannelAgent*)>& aFunc) {
   MOZ_ASSERT(aWindow);
 
-  nsCOMPtr<nsPIDOMWindowOuter> topWindow = aWindow->GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topWindow = aWindow->GetInProcessScriptableTop();
   if (!topWindow) {
     return;
   }
@@ -458,7 +459,7 @@ void AudioChannelService::SetWindowAudioCaptured(nsPIDOMWindowOuter* aWindow,
            "aCapture = %d\n",
            aWindow, aCapture));
 
-  nsCOMPtr<nsPIDOMWindowOuter> topWindow = aWindow->GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topWindow = aWindow->GetInProcessScriptableTop();
   if (!topWindow) {
     return;
   }
@@ -515,7 +516,7 @@ AudioChannelService::AudioChannelWindow* AudioChannelService::GetWindowData(
 bool AudioChannelService::IsWindowActive(nsPIDOMWindowOuter* aWindow) {
   MOZ_ASSERT(NS_IsMainThread());
 
-  auto* window = nsPIDOMWindowOuter::From(aWindow)->GetScriptableTop();
+  auto* window = nsPIDOMWindowOuter::From(aWindow)->GetInProcessScriptableTop();
   if (!window) {
     return false;
   }
@@ -546,7 +547,7 @@ void AudioChannelService::NotifyMediaResumedFromBlock(
     nsPIDOMWindowOuter* aWindow) {
   MOZ_ASSERT(aWindow);
 
-  nsCOMPtr<nsPIDOMWindowOuter> topWindow = aWindow->GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topWindow = aWindow->GetInProcessScriptableTop();
   if (!topWindow) {
     return;
   }
diff --git a/dom/base/DocGroup.cpp b/dom/base/DocGroup.cpp
index 87d6f9bc9d6c..82934edc7d08 100644
--- a/dom/base/DocGroup.cpp
+++ b/dom/base/DocGroup.cpp
@@ -106,7 +106,7 @@ RefPtr<PerformanceInfoPromise> DocGroup::ReportPerformanceInfo() {
     if (!win) {
       continue;
     }
-    top = win->GetTop();
+    top = win->GetInProcessTop();
     if (!top) {
       continue;
     }
diff --git a/dom/base/Document.cpp b/dom/base/Document.cpp
index 82eec7b0ff63..8712bc6eda23 100644
--- a/dom/base/Document.cpp
+++ b/dom/base/Document.cpp
@@ -2249,7 +2249,7 @@ bool Document::IsVisibleConsideringAncestors() const {
     if (!parent->IsVisible()) {
       return false;
     }
-  } while ((parent = parent->GetParentDocument()));
+  } while ((parent = parent->GetInProcessParentDocument()));
 
   return true;
 }
@@ -2478,11 +2478,12 @@ already_AddRefed<nsIPrincipal> Document::MaybeDowngradePrincipal(
 
   if (nsContentUtils::IsSystemPrincipal(aPrincipal)) {
     // We basically want the parent document here, but because this is very
-    // early in the load, GetParentDocument() returns null, so we use the
-    // docshell hierarchy to get this information instead.
+    // early in the load, GetInProcessParentDocument() returns null, so we use
+    // the docshell hierarchy to get this information instead.
     if (mDocumentContainer) {
       nsCOMPtr<nsIDocShellTreeItem> parentDocShellItem;
-      mDocumentContainer->GetParent(getter_AddRefs(parentDocShellItem));
+      mDocumentContainer->GetInProcessParent(
+          getter_AddRefs(parentDocShellItem));
       nsCOMPtr<nsIDocShell> parentDocShell =
           do_QueryInterface(parentDocShellItem);
       if (parentDocShell) {
@@ -2822,7 +2823,7 @@ static void WarnIfSandboxIneffective(nsIDocShell* aDocShell,
       !(aSandboxFlags & SANDBOXED_SCRIPTS) &&
       !(aSandboxFlags & SANDBOXED_ORIGIN)) {
     nsCOMPtr<nsIDocShellTreeItem> parentAsItem;
-    aDocShell->GetSameTypeParent(getter_AddRefs(parentAsItem));
+    aDocShell->GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
     nsCOMPtr<nsIDocShell> parentDocShell = do_QueryInterface(parentAsItem);
     if (!parentDocShell) {
       return;
@@ -2830,7 +2831,8 @@ static void WarnIfSandboxIneffective(nsIDocShell* aDocShell,
 
     // Don't warn if our parent is not the top-level document.
     nsCOMPtr<nsIDocShellTreeItem> grandParentAsItem;
-    parentDocShell->GetSameTypeParent(getter_AddRefs(grandParentAsItem));
+    parentDocShell->GetInProcessSameTypeParent(
+        getter_AddRefs(grandParentAsItem));
     if (grandParentAsItem) {
       return;
     }
@@ -2966,7 +2968,7 @@ nsresult Document::StartDocumentLoad(const char* aCommand, nsIChannel* aChannel,
   nsCOMPtr<nsIDocShellTreeItem> treeItem = this->GetDocShell();
   if (treeItem) {
     nsCOMPtr<nsIDocShellTreeItem> sameTypeParent;
-    treeItem->GetSameTypeParent(getter_AddRefs(sameTypeParent));
+    treeItem->GetInProcessSameTypeParent(getter_AddRefs(sameTypeParent));
     if (sameTypeParent) {
       Document* doc = sameTypeParent->GetDocument();
       mBlockAllMixedContent = doc->GetBlockAllMixedContent(false);
@@ -3009,7 +3011,7 @@ nsresult Document::StartDocumentLoad(const char* aCommand, nsIChannel* aChannel,
     rv = loadInfo->GetCookieSettings(getter_AddRefs(mCookieSettings));
     NS_ENSURE_SUCCESS(rv, rv);
   } else {
-    nsCOMPtr<Document> parentDocument = GetParentDocument();
+    nsCOMPtr<Document> parentDocument = GetInProcessParentDocument();
     if (parentDocument) {
       mCookieSettings = parentDocument->CookieSettings();
     }
@@ -3826,7 +3828,7 @@ bool Document::HasFocus(ErrorResult& rv) const {
 
   // Are we an ancestor of the focused DOMWindow?
   for (Document* currentDoc = piWindow->GetDoc(); currentDoc;
-       currentDoc = currentDoc->GetParentDocument()) {
+       currentDoc = currentDoc->GetInProcessParentDocument()) {
     if (currentDoc == this) {
       // Yes, we are an ancestor
       return true;
@@ -4939,7 +4941,7 @@ void Document::QueryCommandValue(const nsAString& aHTMLCommandName,
 }
 
 bool Document::IsEditingOnAfterFlush() {
-  RefPtr<Document> doc = GetParentDocument();
+  RefPtr<Document> doc = GetInProcessParentDocument();
   if (doc) {
     // Make sure frames are up to date, since that can affect whether
     // we're editable.
@@ -7101,7 +7103,7 @@ void Document::DispatchContentLoadedEvents() {
         }
       }
 
-      parent = parent->GetParentDocument();
+      parent = parent->GetInProcessParentDocument();
     } while (parent);
   }
 
@@ -9337,7 +9339,7 @@ nsINode* Document::AdoptNode(nsINode& aAdoptedNode, ErrorResult& rv) {
             return nullptr;
           }
         }
-      } while ((doc = doc->GetParentDocument()));
+      } while ((doc = doc->GetInProcessParentDocument()));
 
       // Remove from parent.
       nsCOMPtr<nsINode> parent = adoptedNode->GetParentNode();
@@ -11728,7 +11730,7 @@ static already_AddRefed<nsPIDOMWindowOuter> FindTopWindowForElement(
   }
 
   // Trying to find the top window (equivalent to window.top).
-  if (nsCOMPtr<nsPIDOMWindowOuter> top = window->GetTop()) {
+  if (nsCOMPtr<nsPIDOMWindowOuter> top = window->GetInProcessTop()) {
     window = top.forget();
   }
   return window.forget();
@@ -12921,7 +12923,7 @@ class PendingFullscreenChangeList {
           }
           while (docShell && docShell != mRootShellForIteration) {
             nsCOMPtr<nsIDocShellTreeItem> parent;
-            docShell->GetParent(getter_AddRefs(parent));
+            docShell->GetInProcessParent(getter_AddRefs(parent));
             docShell = parent.forget();
           }
           if (docShell) {
@@ -13165,7 +13167,7 @@ void Document::RestorePreviousFullscreenState(UniquePtr<FullscreenExit> aExit) {
 
   Document* doc = fullScreenDoc;
   // Collect all subdocuments.
-  for (; doc != this; doc = doc->GetParentDocument()) {
+  for (; doc != this; doc = doc->GetInProcessParentDocument()) {
     Element* fsElement = doc->FullscreenStackTop();
     MOZ_ASSERT(fsElement,
                "Parent document of "
@@ -13174,7 +13176,7 @@ void Document::RestorePreviousFullscreenState(UniquePtr<FullscreenExit> aExit) {
   }
   MOZ_ASSERT(doc == this, "Must have reached this doc");
   // Collect all ancestor documents which we are going to change.
-  for (; doc; doc = doc->GetParentDocument()) {
+  for (; doc; doc = doc->GetInProcessParentDocument()) {
     MOZ_ASSERT(!doc->mFullscreenStack.IsEmpty(),
                "Ancestor of fullscreen document must also be in fullscreen");
     Element* fsElement = doc->FullscreenStackTop();
@@ -13194,7 +13196,7 @@ void Document::RestorePreviousFullscreenState(UniquePtr<FullscreenExit> aExit) {
   }
 
   Document* lastDoc = exitElements.LastElement()->OwnerDoc();
-  if (!lastDoc->GetParentDocument() &&
+  if (!lastDoc->GetInProcessParentDocument() &&
       lastDoc->mFullscreenStack.Length() == 1) {
     // If we are fully exiting fullscreen, don't touch anything here,
     // just wait for the window to get out from fullscreen first.
@@ -13218,7 +13220,7 @@ void Document::RestorePreviousFullscreenState(UniquePtr<FullscreenExit> aExit) {
     newFullscreenDoc = lastDoc;
   } else {
     lastDoc->CleanupFullscreenState();
-    newFullscreenDoc = lastDoc->GetParentDocument();
+    newFullscreenDoc = lastDoc->GetInProcessParentDocument();
   }
   // Dispatch the fullscreenchange event to all document listed. Note
   // that the loop order is reversed so that events are dispatched in
@@ -13707,7 +13709,7 @@ bool Document::ApplyFullscreen(UniquePtr<FullscreenRequest> aRequest) {
     if (child == fullScreenRootDoc) {
       break;
     }
-    Document* parent = child->GetParentDocument();
+    Document* parent = child->GetInProcessParentDocument();
     Element* element = parent->FindContentForSubDocument(child);
     if (parent->FullscreenStackPush(element)) {
       changed.AppendElement(parent);
@@ -13841,7 +13843,7 @@ static const char* GetPointerLockError(Element* aElement, Element* aCurrentLock,
     return "PointerLockDeniedHidden";
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> top = ownerWindow->GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> top = ownerWindow->GetInProcessScriptableTop();
   if (!top || !top->GetExtantDoc() || top->GetExtantDoc()->Hidden()) {
     return "PointerLockDeniedHidden";
   }
@@ -14322,7 +14324,7 @@ Document* Document::GetTopLevelContentDocument() {
       return nullptr;
     }
 
-    parent = parent->GetParentDocument();
+    parent = parent->GetInProcessParentDocument();
   } while (parent);
 
   return parent;
@@ -14356,7 +14358,7 @@ const Document* Document::GetTopLevelContentDocument() const {
       return nullptr;
     }
 
-    parent = parent->GetParentDocument();
+    parent = parent->GetInProcessParentDocument();
   } while (parent);
 
   return parent;
@@ -14750,7 +14752,7 @@ nsAutoSyncOperation::nsAutoSyncOperation(Document* aDoc) {
   }
   if (aDoc) {
     if (nsPIDOMWindowOuter* win = aDoc->GetWindow()) {
-      if (nsCOMPtr<nsPIDOMWindowOuter> top = win->GetTop()) {
+      if (nsCOMPtr<nsPIDOMWindowOuter> top = win->GetInProcessTop()) {
         nsCOMPtr<Document> doc = top->GetExtantDoc();
         MarkDocumentTreeToBeInSyncOperation(doc, &mDocuments);
       }
@@ -15175,7 +15177,7 @@ Document* Document::GetSameTypeParentDocument() {
   }
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  current->GetSameTypeParent(getter_AddRefs(parent));
+  current->GetInProcessSameTypeParent(getter_AddRefs(parent));
   if (!parent) {
     return nullptr;
   }
@@ -15282,9 +15284,10 @@ bool Document::IsThirdPartyForFlashClassifier() {
   }
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  nsresult rv = docshell->GetSameTypeParent(getter_AddRefs(parent));
-  MOZ_ASSERT(NS_SUCCEEDED(rv),
-             "nsIDocShellTreeItem::GetSameTypeParent should never fail");
+  nsresult rv = docshell->GetInProcessSameTypeParent(getter_AddRefs(parent));
+  MOZ_ASSERT(
+      NS_SUCCEEDED(rv),
+      "nsIDocShellTreeItem::GetInProcessSameTypeParent should never fail");
   bool isTopLevel = !parent;
 
   if (isTopLevel) {
@@ -15292,7 +15295,7 @@ bool Document::IsThirdPartyForFlashClassifier() {
     return mIsThirdPartyForFlashClassifier.value();
   }
 
-  nsCOMPtr<Document> parentDocument = GetParentDocument();
+  nsCOMPtr<Document> parentDocument = GetInProcessParentDocument();
   if (!parentDocument) {
     // Failure
     mIsThirdPartyForFlashClassifier.emplace(true);
@@ -15355,7 +15358,7 @@ FlashClassification Document::DocumentFlashClassificationInternal() {
     return classification;
   }
 
-  Document* parentDocument = GetParentDocument();
+  Document* parentDocument = GetInProcessParentDocument();
   if (!parentDocument) {
     return FlashClassification::Denied;
   }
@@ -15503,7 +15506,7 @@ already_AddRefed<mozilla::dom::Promise> Document::RequestStorageAccess(
   }
 
   // Step 7. If the sub frame's parent frame is not the top frame, reject.
-  Document* parent = GetParentDocument();
+  Document* parent = GetInProcessParentDocument();
   if (parent && !parent->IsTopLevelContentDocument()) {
     promise->MaybeRejectWithUndefined();
     return promise.forget();
diff --git a/dom/base/Document.h b/dom/base/Document.h
index 1c3e49e39083..4c6873a25ec3 100644
--- a/dom/base/Document.h
+++ b/dom/base/Document.h
@@ -1447,7 +1447,7 @@ class Document : public nsINode,
    * unless this document is within a compound document and has a
    * parent. Note that this parent chain may cross chrome boundaries.
    */
-  Document* GetParentDocument() const { return mParentDocument; }
+  Document* GetInProcessParentDocument() const { return mParentDocument; }
 
   /**
    * Set the parent document of this document.
@@ -3864,8 +3864,8 @@ class Document : public nsINode,
    * up-to-date layout information.
    */
   bool StyleOrLayoutObservablyDependsOnParentDocumentLayout() const {
-    return GetParentDocument() &&
-           GetDocGroup() == GetParentDocument()->GetDocGroup();
+    return GetInProcessParentDocument() &&
+           GetDocGroup() == GetInProcessParentDocument()->GetDocGroup();
   }
 
   void AddIntersectionObserver(DOMIntersectionObserver* aObserver) {
diff --git a/dom/base/PostMessageEvent.cpp b/dom/base/PostMessageEvent.cpp
index 3451c8402f4b..4b5399f5dd60 100644
--- a/dom/base/PostMessageEvent.cpp
+++ b/dom/base/PostMessageEvent.cpp
@@ -78,7 +78,7 @@ PostMessageEvent::Run() {
   // be delivered in the same order they were posted, regardless of which window
   // they were posted to.
   if (nsCOMPtr<nsPIDOMWindowOuter> topWindow =
-          targetWindow->GetOuterWindow()->GetTop()) {
+          targetWindow->GetOuterWindow()->GetInProcessTop()) {
     if (nsCOMPtr<nsPIDOMWindowInner> topInner =
             topWindow->GetCurrentInnerWindow()) {
       if (topInner->GetExtantDoc() &&
diff --git a/dom/base/ScreenOrientation.cpp b/dom/base/ScreenOrientation.cpp
index daafecffe41c..592043f52a1b 100644
--- a/dom/base/ScreenOrientation.cpp
+++ b/dom/base/ScreenOrientation.cpp
@@ -260,10 +260,11 @@ static inline void AbortOrientationPromises(nsIDocShell* aDocShell) {
   }
 
   int32_t childCount;
-  aDocShell->GetChildCount(&childCount);
+  aDocShell->GetInProcessChildCount(&childCount);
   for (int32_t i = 0; i < childCount; i++) {
     nsCOMPtr<nsIDocShellTreeItem> child;
-    if (NS_SUCCEEDED(aDocShell->GetChildAt(i, getter_AddRefs(child)))) {
+    if (NS_SUCCEEDED(
+            aDocShell->GetInProcessChildAt(i, getter_AddRefs(child)))) {
       nsCOMPtr<nsIDocShell> childShell(do_QueryInterface(child));
       if (childShell) {
         AbortOrientationPromises(childShell);
@@ -313,7 +314,7 @@ already_AddRefed<Promise> ScreenOrientation::LockInternal(
   }
 
   nsCOMPtr<nsIDocShellTreeItem> root;
-  docShell->GetSameTypeRootTreeItem(getter_AddRefs(root));
+  docShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   nsCOMPtr<nsIDocShell> rootShell(do_QueryInterface(root));
   if (!rootShell) {
     aRv.Throw(NS_ERROR_UNEXPECTED);
diff --git a/dom/base/TabGroup.cpp b/dom/base/TabGroup.cpp
index e608b996d365..c1f0ee8ce394 100644
--- a/dom/base/TabGroup.cpp
+++ b/dom/base/TabGroup.cpp
@@ -215,7 +215,7 @@ nsresult TabGroup::FindItemWithName(const nsAString& aName,
 
   for (nsPIDOMWindowOuter* outerWindow : mWindows) {
     // Ignore non-toplevel windows
-    if (outerWindow->GetScriptableParentOrNull()) {
+    if (outerWindow->GetInProcessScriptableParentOrNull()) {
       continue;
     }
 
@@ -230,7 +230,7 @@ nsresult TabGroup::FindItemWithName(const nsAString& aName,
     }
 
     nsCOMPtr<nsIDocShellTreeItem> root;
-    docshell->GetSameTypeRootTreeItem(getter_AddRefs(root));
+    docshell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
     MOZ_RELEASE_ASSERT(docshell == root);
     if (root && aRequestor != root) {
       root->FindItemWithName(aName, aRequestor, aOriginalRequestor,
@@ -250,7 +250,7 @@ nsTArray<nsPIDOMWindowOuter*> TabGroup::GetTopLevelWindows() const {
 
   for (nsPIDOMWindowOuter* outerWindow : mWindows) {
     if (outerWindow->GetDocShell() &&
-        !outerWindow->GetScriptableParentOrNull()) {
+        !outerWindow->GetInProcessScriptableParentOrNull()) {
       array.AppendElement(outerWindow);
     }
   }
diff --git a/dom/base/ThirdPartyUtil.cpp b/dom/base/ThirdPartyUtil.cpp
index 0f4a6e7d390d..f467262ecbdb 100644
--- a/dom/base/ThirdPartyUtil.cpp
+++ b/dom/base/ThirdPartyUtil.cpp
@@ -197,9 +197,9 @@ ThirdPartyUtil::IsThirdPartyWindow(mozIDOMWindowProxy* aWindow, nsIURI* aURI,
 
   nsPIDOMWindowOuter* current = nsPIDOMWindowOuter::From(aWindow);
   do {
-    // We use GetScriptableParent rather than GetParent because we consider
-    // <iframe mozbrowser> to be a top-level frame.
-    nsPIDOMWindowOuter* parent = current->GetScriptableParent();
+    // We use GetInProcessScriptableParent rather than GetParent because we
+    // consider <iframe mozbrowser> to be a top-level frame.
+    nsPIDOMWindowOuter* parent = current->GetInProcessScriptableParent();
     // We don't use SameCOMIdentity here since we know that nsPIDOMWindowOuter
     // is only implemented by nsGlobalWindowOuter, so different objects of that
     // type will not have different nsISupports COM identities, and checking the
diff --git a/dom/base/nsCCUncollectableMarker.cpp b/dom/base/nsCCUncollectableMarker.cpp
index 5cafd180c4af..022197076431 100644
--- a/dom/base/nsCCUncollectableMarker.cpp
+++ b/dom/base/nsCCUncollectableMarker.cpp
@@ -257,10 +257,10 @@ void MarkDocShell(nsIDocShellTreeItem* aNode, bool aCleanupJS) {
   }
 
   int32_t i, childCount;
-  aNode->GetChildCount(&childCount);
+  aNode->GetInProcessChildCount(&childCount);
   for (i = 0; i < childCount; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> child;
-    aNode->GetChildAt(i, getter_AddRefs(child));
+    aNode->GetInProcessChildAt(i, getter_AddRefs(child));
     MarkDocShell(child, aCleanupJS);
   }
 }
diff --git a/dom/base/nsContentPermissionHelper.cpp b/dom/base/nsContentPermissionHelper.cpp
index b3accf7620de..4ee8be31a6bc 100644
--- a/dom/base/nsContentPermissionHelper.cpp
+++ b/dom/base/nsContentPermissionHelper.cpp
@@ -515,7 +515,7 @@ nsContentPermissionRequester::GetOnVisibilityChange(
 static nsIPrincipal* GetTopLevelPrincipal(nsPIDOMWindowInner* aWindow) {
   MOZ_ASSERT(aWindow);
 
-  nsPIDOMWindowOuter* top = aWindow->GetScriptableTop();
+  nsPIDOMWindowOuter* top = aWindow->GetInProcessScriptableTop();
   if (!top) {
     return nullptr;
   }
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 29eb948d9f55..e4b9fe1f4e4f 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -2184,7 +2184,7 @@ nsINode* nsContentUtils::GetCrossDocParentNode(nsINode* aChild) {
   }
 
   Document* doc = aChild->AsDocument();
-  Document* parentDoc = doc->GetParentDocument();
+  Document* parentDoc = doc->GetInProcessParentDocument();
   return parentDoc ? parentDoc->FindContentForSubDocument(doc) : nullptr;
 }
 
@@ -3767,7 +3767,7 @@ bool nsContentUtils::IsChildOfSameType(Document* aDoc) {
   nsCOMPtr<nsIDocShellTreeItem> docShellAsItem(aDoc->GetDocShell());
   nsCOMPtr<nsIDocShellTreeItem> sameTypeParent;
   if (docShellAsItem) {
-    docShellAsItem->GetSameTypeParent(getter_AddRefs(sameTypeParent));
+    docShellAsItem->GetInProcessSameTypeParent(getter_AddRefs(sameTypeParent));
   }
   return sameTypeParent != nullptr;
 }
@@ -5420,7 +5420,7 @@ bool nsContentUtils::CheckForSubFrameDrop(nsIDragSession* aDragSession,
     // Get each successive parent of the source document and compare it to
     // the drop document. If they match, then this is a drag from a child frame.
     do {
-      doc = doc->GetParentDocument();
+      doc = doc->GetInProcessParentDocument();
       if (doc == targetDoc) {
         // The drag is from a child frame.
         return true;
@@ -6052,10 +6052,11 @@ void nsContentUtils::FlushLayoutForTree(nsPIDOMWindowOuter* aWindow) {
 
   if (nsCOMPtr<nsIDocShell> docShell = aWindow->GetDocShell()) {
     int32_t i = 0, i_end;
-    docShell->GetChildCount(&i_end);
+    docShell->GetInProcessChildCount(&i_end);
     for (; i < i_end; ++i) {
       nsCOMPtr<nsIDocShellTreeItem> item;
-      if (docShell->GetChildAt(i, getter_AddRefs(item)) == NS_OK && item) {
+      if (docShell->GetInProcessChildAt(i, getter_AddRefs(item)) == NS_OK &&
+          item) {
         if (nsCOMPtr<nsPIDOMWindowOuter> win = item->GetWindow()) {
           FlushLayoutForTree(win);
         }
@@ -6131,7 +6132,7 @@ PresShell* nsContentUtils::FindPresShellForDocument(const Document* aDocument) {
       return presShell;
     }
     nsCOMPtr<nsIDocShellTreeItem> parent;
-    docShellTreeItem->GetParent(getter_AddRefs(parent));
+    docShellTreeItem->GetInProcessParent(getter_AddRefs(parent));
     docShellTreeItem = parent;
   }
 
@@ -6517,8 +6518,8 @@ Document* nsContentUtils::GetRootDocument(Document* aDoc) {
     return nullptr;
   }
   Document* doc = aDoc;
-  while (doc->GetParentDocument()) {
-    doc = doc->GetParentDocument();
+  while (doc->GetInProcessParentDocument()) {
+    doc = doc->GetInProcessParentDocument();
   }
   return doc;
 }
@@ -6536,8 +6537,8 @@ bool nsContentUtils::IsInPointerLockContext(nsPIDOMWindowOuter* aWin) {
   }
 
   nsCOMPtr<nsPIDOMWindowOuter> lockTop =
-      pointerLockedDoc->GetWindow()->GetScriptableTop();
-  nsCOMPtr<nsPIDOMWindowOuter> top = aWin->GetScriptableTop();
+      pointerLockedDoc->GetWindow()->GetInProcessScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> top = aWin->GetInProcessScriptableTop();
 
   return top == lockTop;
 }
@@ -6933,7 +6934,7 @@ bool nsContentUtils::PrefetchPreloadEnabled(nsIDocShell* aDocShell) {
       return false;  // do not prefetch, preload, preconnect from mailnews
     }
 
-    docshell->GetParent(getter_AddRefs(parentItem));
+    docshell->GetInProcessParent(getter_AddRefs(parentItem));
     if (parentItem) {
       docshell = do_QueryInterface(parentItem);
       if (!docshell) {
@@ -7814,11 +7815,11 @@ void nsContentUtils::FirePageHideEvent(nsIDocShellTreeItem* aItem,
   doc->OnPageHide(true, aChromeEventHandler, aOnlySystemGroup);
 
   int32_t childCount = 0;
-  aItem->GetChildCount(&childCount);
+  aItem->GetInProcessChildCount(&childCount);
   AutoTArray<nsCOMPtr<nsIDocShellTreeItem>, 8> kids;
   kids.AppendElements(childCount);
   for (int32_t i = 0; i < childCount; ++i) {
-    aItem->GetChildAt(i, getter_AddRefs(kids[i]));
+    aItem->GetInProcessChildAt(i, getter_AddRefs(kids[i]));
   }
 
   for (uint32_t i = 0; i < kids.Length(); ++i) {
@@ -7838,11 +7839,11 @@ void nsContentUtils::FirePageShowEvent(nsIDocShellTreeItem* aItem,
                                        bool aFireIfShowing,
                                        bool aOnlySystemGroup) {
   int32_t childCount = 0;
-  aItem->GetChildCount(&childCount);
+  aItem->GetInProcessChildCount(&childCount);
   AutoTArray<nsCOMPtr<nsIDocShellTreeItem>, 8> kids;
   kids.AppendElements(childCount);
   for (int32_t i = 0; i < childCount; ++i) {
-    aItem->GetChildAt(i, getter_AddRefs(kids[i]));
+    aItem->GetInProcessChildAt(i, getter_AddRefs(kids[i]));
   }
 
   for (uint32_t i = 0; i < kids.Length(); ++i) {
@@ -8754,7 +8755,7 @@ void nsContentUtils::GetPresentationURL(nsIDocShell* aDocShell,
 
   if (XRE_IsContentProcess()) {
     nsCOMPtr<nsIDocShellTreeItem> sameTypeRoot;
-    aDocShell->GetSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
+    aDocShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
     nsCOMPtr<nsIDocShellTreeItem> root;
     aDocShell->GetRootTreeItem(getter_AddRefs(root));
     if (sameTypeRoot.get() == root.get()) {
@@ -9595,7 +9596,7 @@ bool nsContentUtils::ShouldBlockReservedKeys(WidgetKeyboardEvent* aKeyEvent) {
         if (docShell &&
             docShell->ItemType() == nsIDocShellTreeItem::typeContent) {
           nsCOMPtr<nsIDocShellTreeItem> rootItem;
-          docShell->GetSameTypeRootTreeItem(getter_AddRefs(rootItem));
+          docShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(rootItem));
           if (rootItem && rootItem->GetDocument()) {
             principal = rootItem->GetDocument()->NodePrincipal();
           }
diff --git a/dom/base/nsDOMNavigationTiming.cpp b/dom/base/nsDOMNavigationTiming.cpp
index 01ce331679d3..5f753880b436 100644
--- a/dom/base/nsDOMNavigationTiming.cpp
+++ b/dom/base/nsDOMNavigationTiming.cpp
@@ -535,7 +535,8 @@ bool nsDOMNavigationTiming::IsTopLevelContentDocumentInContentProcess() const {
     return false;
   }
   nsCOMPtr<nsIDocShellTreeItem> rootItem;
-  Unused << mDocShell->GetSameTypeRootTreeItem(getter_AddRefs(rootItem));
+  Unused << mDocShell->GetInProcessSameTypeRootTreeItem(
+      getter_AddRefs(rootItem));
   if (rootItem.get() != static_cast<nsIDocShellTreeItem*>(mDocShell.get())) {
     return false;
   }
diff --git a/dom/base/nsFocusManager.cpp b/dom/base/nsFocusManager.cpp
index 4130cd4c75e5..d0709605eecd 100644
--- a/dom/base/nsFocusManager.cpp
+++ b/dom/base/nsFocusManager.cpp
@@ -973,7 +973,7 @@ nsFocusManager::WindowHidden(mozIDOMWindowProxy* aWindow) {
         mFocusedWindow ? mFocusedWindow->GetDocShell() : nullptr;
     if (dsti) {
       nsCOMPtr<nsIDocShellTreeItem> parentDsti;
-      dsti->GetParent(getter_AddRefs(parentDsti));
+      dsti->GetInProcessParent(getter_AddRefs(parentDsti));
       if (parentDsti) {
         if (nsCOMPtr<nsPIDOMWindowOuter> parentWindow = parentDsti->GetWindow())
           parentWindow->SetFocusedElement(nullptr);
@@ -1188,7 +1188,7 @@ void nsFocusManager::SetFocusInner(Element* aNewContent, int32_t aFlags,
     if (beingDestroyed) return;
 
     nsCOMPtr<nsIDocShellTreeItem> parentDsti;
-    docShell->GetParent(getter_AddRefs(parentDsti));
+    docShell->GetInProcessParent(getter_AddRefs(parentDsti));
     docShell = do_QueryInterface(parentDsti);
   }
 
@@ -1358,7 +1358,7 @@ bool nsFocusManager::IsSameOrAncestor(nsPIDOMWindowOuter* aPossibleAncestor,
   while (dsti) {
     if (dsti == ancestordsti) return true;
     nsCOMPtr<nsIDocShellTreeItem> parentDsti;
-    dsti->GetParent(getter_AddRefs(parentDsti));
+    dsti->GetInProcessParent(getter_AddRefs(parentDsti));
     dsti.swap(parentDsti);
   }
 
@@ -1379,13 +1379,13 @@ already_AddRefed<nsPIDOMWindowOuter> nsFocusManager::GetCommonAncestor(
   do {
     parents1.AppendElement(dsti1);
     nsCOMPtr<nsIDocShellTreeItem> parentDsti1;
-    dsti1->GetParent(getter_AddRefs(parentDsti1));
+    dsti1->GetInProcessParent(getter_AddRefs(parentDsti1));
     dsti1.swap(parentDsti1);
   } while (dsti1);
   do {
     parents2.AppendElement(dsti2);
     nsCOMPtr<nsIDocShellTreeItem> parentDsti2;
-    dsti2->GetParent(getter_AddRefs(parentDsti2));
+    dsti2->GetInProcessParent(getter_AddRefs(parentDsti2));
     dsti2.swap(parentDsti2);
   } while (dsti2);
 
@@ -1419,7 +1419,7 @@ void nsFocusManager::AdjustWindowFocus(nsPIDOMWindowOuter* aWindow,
     nsCOMPtr<nsIDocShellTreeItem> dsti = window->GetDocShell();
     if (!dsti) return;
     nsCOMPtr<nsIDocShellTreeItem> parentDsti;
-    dsti->GetParent(getter_AddRefs(parentDsti));
+    dsti->GetInProcessParent(getter_AddRefs(parentDsti));
     if (!parentDsti) {
       return;
     }
@@ -4020,7 +4020,7 @@ void nsFocusManager::SetFocusedWindowInternal(nsPIDOMWindowOuter* aWindow) {
   if (aWindow && aWindow != mFocusedWindow) {
     const TimeStamp now(TimeStamp::Now());
     for (Document* doc = aWindow->GetExtantDoc(); doc;
-         doc = doc->GetParentDocument()) {
+         doc = doc->GetInProcessParentDocument()) {
       doc->SetLastFocusTime(now);
     }
   }
diff --git a/dom/base/nsFrameLoader.cpp b/dom/base/nsFrameLoader.cpp
index 45007353c909..fda8676c4483 100644
--- a/dom/base/nsFrameLoader.cpp
+++ b/dom/base/nsFrameLoader.cpp
@@ -732,10 +732,10 @@ static void SetTreeOwnerAndChromeEventHandlerOnDocshellTree(
   aItem->SetTreeOwner(aOwner);
 
   int32_t childCount = 0;
-  aItem->GetChildCount(&childCount);
+  aItem->GetInProcessChildCount(&childCount);
   for (int32_t i = 0; i < childCount; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> item;
-    aItem->GetChildAt(i, getter_AddRefs(item));
+    aItem->GetInProcessChildAt(i, getter_AddRefs(item));
     if (aHandler) {
       nsCOMPtr<nsIDocShell> shell(do_QueryInterface(item));
       shell->SetChromeEventHandler(aHandler);
@@ -763,7 +763,7 @@ static bool CheckDocShellType(mozilla::dom::Element* aOwnerContent,
   }
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  aDocShell->GetParent(getter_AddRefs(parent));
+  aDocShell->GetInProcessParent(getter_AddRefs(parent));
 
   return parent && parent->ItemType() == aDocShell->ItemType();
 }
@@ -798,11 +798,11 @@ void nsFrameLoader::AddTreeItemToTreeOwner(nsIDocShellTreeItem* aItem,
 static bool AllDescendantsOfType(nsIDocShellTreeItem* aParentItem,
                                  int32_t aType) {
   int32_t childCount = 0;
-  aParentItem->GetChildCount(&childCount);
+  aParentItem->GetInProcessChildCount(&childCount);
 
   for (int32_t i = 0; i < childCount; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> kid;
-    aParentItem->GetChildAt(i, getter_AddRefs(kid));
+    aParentItem->GetInProcessChildAt(i, getter_AddRefs(kid));
 
     if (kid->ItemType() != aType || !AllDescendantsOfType(kid, aType)) {
       return false;
@@ -1441,8 +1441,10 @@ nsresult nsFrameLoader::SwapWithOtherLoader(nsFrameLoader* aOther,
   // frameloaders that don't correspond to root same-type docshells,
   // unless both roots have session history disabled.
   nsCOMPtr<nsIDocShellTreeItem> ourRootTreeItem, otherRootTreeItem;
-  ourDocshell->GetSameTypeRootTreeItem(getter_AddRefs(ourRootTreeItem));
-  otherDocshell->GetSameTypeRootTreeItem(getter_AddRefs(otherRootTreeItem));
+  ourDocshell->GetInProcessSameTypeRootTreeItem(
+      getter_AddRefs(ourRootTreeItem));
+  otherDocshell->GetInProcessSameTypeRootTreeItem(
+      getter_AddRefs(otherRootTreeItem));
   nsCOMPtr<nsIWebNavigation> ourRootWebnav = do_QueryInterface(ourRootTreeItem);
   nsCOMPtr<nsIWebNavigation> otherRootWebnav =
       do_QueryInterface(otherRootTreeItem);
@@ -1486,8 +1488,8 @@ nsresult nsFrameLoader::SwapWithOtherLoader(nsFrameLoader* aOther,
   // Note: it's OK to have null treeowners.
 
   nsCOMPtr<nsIDocShellTreeItem> ourParentItem, otherParentItem;
-  ourDocshell->GetParent(getter_AddRefs(ourParentItem));
-  otherDocshell->GetParent(getter_AddRefs(otherParentItem));
+  ourDocshell->GetInProcessParent(getter_AddRefs(ourParentItem));
+  otherDocshell->GetInProcessParent(getter_AddRefs(otherParentItem));
   if (!ourParentItem || !otherParentItem) {
     return NS_ERROR_NOT_IMPLEMENTED;
   }
@@ -1526,9 +1528,10 @@ nsresult nsFrameLoader::SwapWithOtherLoader(nsFrameLoader* aOther,
     return NS_ERROR_NOT_IMPLEMENTED;
   }
 
-  nsCOMPtr<Document> ourParentDocument = ourChildDocument->GetParentDocument();
+  nsCOMPtr<Document> ourParentDocument =
+      ourChildDocument->GetInProcessParentDocument();
   nsCOMPtr<Document> otherParentDocument =
-      otherChildDocument->GetParentDocument();
+      otherChildDocument->GetInProcessParentDocument();
 
   // Make sure to swap docshells between the two frames.
   Document* ourDoc = ourContent->GetComposedDoc();
@@ -1791,7 +1794,7 @@ void nsFrameLoader::StartDestroy() {
   if (mIsTopLevelContent) {
     if (GetDocShell()) {
       nsCOMPtr<nsIDocShellTreeItem> parentItem;
-      GetDocShell()->GetParent(getter_AddRefs(parentItem));
+      GetDocShell()->GetInProcessParent(getter_AddRefs(parentItem));
       nsCOMPtr<nsIDocShellTreeOwner> owner = do_GetInterface(parentItem);
       if (owner) {
         owner->ContentShellRemoved(GetDocShell());
@@ -2183,7 +2186,7 @@ nsresult nsFrameLoader::MaybeCreateDocShell() {
     docShell->SetFrameType(nsIDocShell::FRAME_TYPE_BROWSER);
   } else {
     nsCOMPtr<nsIDocShellTreeItem> parentCheck;
-    docShell->GetSameTypeParent(getter_AddRefs(parentCheck));
+    docShell->GetInProcessSameTypeParent(getter_AddRefs(parentCheck));
     if (!!parentCheck) {
       docShell->SetIsFrame();
     }
@@ -2339,7 +2342,7 @@ nsresult nsFrameLoader::CheckForRecursiveLoad(nsIURI* aURI) {
   // Bug 8065: Don't exceed some maximum depth in content frames
   // (MAX_DEPTH_CONTENT_FRAMES)
   nsCOMPtr<nsIDocShellTreeItem> parentAsItem;
-  GetDocShell()->GetSameTypeParent(getter_AddRefs(parentAsItem));
+  GetDocShell()->GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
   int32_t depth = 0;
   while (parentAsItem) {
     ++depth;
@@ -2353,7 +2356,7 @@ nsresult nsFrameLoader::CheckForRecursiveLoad(nsIURI* aURI) {
 
     nsCOMPtr<nsIDocShellTreeItem> temp;
     temp.swap(parentAsItem);
-    temp->GetSameTypeParent(getter_AddRefs(parentAsItem));
+    temp->GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
   }
 
   // Bug 136580: Check for recursive frame loading excluding about:srcdoc URIs.
@@ -2371,7 +2374,7 @@ nsresult nsFrameLoader::CheckForRecursiveLoad(nsIURI* aURI) {
     }
   }
   int32_t matchCount = 0;
-  GetDocShell()->GetSameTypeParent(getter_AddRefs(parentAsItem));
+  GetDocShell()->GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
   while (parentAsItem) {
     // Check the parent URI with the URI we're loading
     nsCOMPtr<nsIWebNavigation> parentAsNav(do_QueryInterface(parentAsItem));
@@ -2398,7 +2401,7 @@ nsresult nsFrameLoader::CheckForRecursiveLoad(nsIURI* aURI) {
     }
     nsCOMPtr<nsIDocShellTreeItem> temp;
     temp.swap(parentAsItem);
-    temp->GetSameTypeParent(getter_AddRefs(parentAsItem));
+    temp->GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
   }
 
   return NS_OK;
@@ -3101,7 +3104,7 @@ void nsFrameLoader::AttributeChanged(mozilla::dom::Element* aElement,
   }
 
   nsCOMPtr<nsIDocShellTreeItem> parentItem;
-  GetDocShell()->GetParent(getter_AddRefs(parentItem));
+  GetDocShell()->GetInProcessParent(getter_AddRefs(parentItem));
   if (!parentItem) {
     return;
   }
diff --git a/dom/base/nsGlobalWindowInner.cpp b/dom/base/nsGlobalWindowInner.cpp
index bd1d660f46c0..0113415913e2 100644
--- a/dom/base/nsGlobalWindowInner.cpp
+++ b/dom/base/nsGlobalWindowInner.cpp
@@ -1843,7 +1843,7 @@ void nsGlobalWindowInner::UpdateParentTarget() {
       nsContentUtils::TryGetBrowserChildGlobal(frameElement);
 
   if (!eventTarget) {
-    nsGlobalWindowOuter* topWin = GetScriptableTopInternal();
+    nsGlobalWindowOuter* topWin = GetInProcessScriptableTopInternal();
     if (topWin) {
       frameElement = topWin->GetFrameElementInternal();
       eventTarget = nsContentUtils::TryGetBrowserChildGlobal(frameElement);
@@ -1897,10 +1897,10 @@ void nsGlobalWindowInner::GetEventTargetParent(EventChainPreVisitor& aVisitor) {
 }
 
 bool nsGlobalWindowInner::DialogsAreBeingAbused() {
-  NS_ASSERTION(
-      GetScriptableTopInternal() &&
-          GetScriptableTopInternal()->GetCurrentInnerWindowInternal() == this,
-      "DialogsAreBeingAbused called with invalid window");
+  NS_ASSERTION(GetInProcessScriptableTopInternal() &&
+                   GetInProcessScriptableTopInternal()
+                           ->GetCurrentInnerWindowInternal() == this,
+               "DialogsAreBeingAbused called with invalid window");
 
   if (mLastDialogQuitTime.IsNull() || nsContentUtils::IsCallerChrome()) {
     return false;
@@ -2087,7 +2087,7 @@ nsIPrincipal* nsGlobalWindowInner::GetPrincipal() {
   // a document into the window.
 
   nsCOMPtr<nsIScriptObjectPrincipal> objPrincipal =
-      do_QueryInterface(GetParentInternal());
+      do_QueryInterface(GetInProcessParentInternal());
 
   if (objPrincipal) {
     return objPrincipal->GetPrincipal();
@@ -2110,7 +2110,7 @@ nsIPrincipal* nsGlobalWindowInner::GetEffectiveStoragePrincipal() {
   // the parent window for the storage principal.
 
   nsCOMPtr<nsIScriptObjectPrincipal> objPrincipal =
-      do_QueryInterface(GetParentInternal());
+      do_QueryInterface(GetInProcessParentInternal());
 
   if (objPrincipal) {
     return objPrincipal->GetEffectiveStoragePrincipal();
@@ -2281,7 +2281,7 @@ bool nsGlobalWindowInner::ShouldReportForServiceWorkerScope(
     const nsAString& aScope) {
   bool result = false;
 
-  nsPIDOMWindowOuter* topOuter = GetScriptableTop();
+  nsPIDOMWindowOuter* topOuter = GetInProcessScriptableTop();
   NS_ENSURE_TRUE(topOuter, false);
 
   nsGlobalWindowInner* topInner =
@@ -2480,7 +2480,8 @@ void nsPIDOMWindowInner::TryToCacheTopInnerWindow() {
 
   MOZ_ASSERT(window);
 
-  if (nsCOMPtr<nsPIDOMWindowOuter> topOutter = window->GetScriptableTop()) {
+  if (nsCOMPtr<nsPIDOMWindowOuter> topOutter =
+          window->GetInProcessScriptableTop()) {
     mTopInnerWindow = topOutter->GetCurrentInnerWindow();
   }
 }
@@ -2625,25 +2626,26 @@ Nullable<WindowProxyHolder> nsGlobalWindowInner::GetParent(
 }
 
 /**
- * GetScriptableParent is called when script reads window.parent.
+ * GetInProcessScriptableParent is called when script reads window.parent.
  *
- * In contrast to GetRealParent, GetScriptableParent respects <iframe
+ * In contrast to GetRealParent, GetInProcessScriptableParent respects <iframe
  * mozbrowser> boundaries, so if |this| is contained by an <iframe
  * mozbrowser>, we will return |this| as its own parent.
  */
-nsPIDOMWindowOuter* nsGlobalWindowInner::GetScriptableParent() {
-  FORWARD_TO_OUTER(GetScriptableParent, (), nullptr);
+nsPIDOMWindowOuter* nsGlobalWindowInner::GetInProcessScriptableParent() {
+  FORWARD_TO_OUTER(GetInProcessScriptableParent, (), nullptr);
 }
 
 /**
- * GetScriptableTop is called when script reads window.top.
+ * GetInProcessScriptableTop is called when script reads window.top.
  *
- * In contrast to GetRealTop, GetScriptableTop respects <iframe mozbrowser>
- * boundaries.  If we encounter a window owned by an <iframe mozbrowser> while
- * walking up the window hierarchy, we'll stop and return that window.
+ * In contrast to GetRealTop, GetInProcessScriptableTop respects <iframe
+ * mozbrowser> boundaries.  If we encounter a window owned by an <iframe
+ * mozbrowser> while walking up the window hierarchy, we'll stop and return that
+ * window.
  */
-nsPIDOMWindowOuter* nsGlobalWindowInner::GetScriptableTop() {
-  FORWARD_TO_OUTER(GetScriptableTop, (), nullptr);
+nsPIDOMWindowOuter* nsGlobalWindowInner::GetInProcessScriptableTop() {
+  FORWARD_TO_OUTER(GetInProcessScriptableTop, (), nullptr);
 }
 
 void nsGlobalWindowInner::GetContent(JSContext* aCx,
@@ -5397,14 +5399,14 @@ nsGlobalWindowInner::CallState nsGlobalWindowInner::CallOnChildren(
   }
 
   int32_t childCount = 0;
-  docShell->GetChildCount(&childCount);
+  docShell->GetInProcessChildCount(&childCount);
 
   // Take a copy of the current children so that modifications to
   // the child list don't affect to the iteration.
   AutoTArray<nsCOMPtr<nsIDocShellTreeItem>, 8> children;
   for (int32_t i = 0; i < childCount; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> childShell;
-    docShell->GetChildAt(i, getter_AddRefs(childShell));
+    docShell->GetInProcessChildAt(i, getter_AddRefs(childShell));
     if (childShell) {
       children.AppendElement(childShell);
     }
@@ -5566,14 +5568,14 @@ nsresult nsGlobalWindowInner::FireDelayedDOMEvents() {
   nsCOMPtr<nsIDocShell> docShell = GetDocShell();
   if (docShell) {
     int32_t childCount = 0;
-    docShell->GetChildCount(&childCount);
+    docShell->GetInProcessChildCount(&childCount);
 
     // Take a copy of the current children so that modifications to
     // the child list don't affect to the iteration.
     AutoTArray<nsCOMPtr<nsIDocShellTreeItem>, 8> children;
     for (int32_t i = 0; i < childCount; ++i) {
       nsCOMPtr<nsIDocShellTreeItem> childShell;
-      docShell->GetChildAt(i, getter_AddRefs(childShell));
+      docShell->GetInProcessChildAt(i, getter_AddRefs(childShell));
       if (childShell) {
         children.AppendElement(childShell);
       }
@@ -5594,13 +5596,13 @@ nsresult nsGlobalWindowInner::FireDelayedDOMEvents() {
 // nsGlobalWindowInner: Window Control Functions
 //*****************************************************************************
 
-nsPIDOMWindowOuter* nsGlobalWindowInner::GetParentInternal() {
+nsPIDOMWindowOuter* nsGlobalWindowInner::GetInProcessParentInternal() {
   nsGlobalWindowOuter* outer = GetOuterWindowInternal();
   if (!outer) {
     // No outer window available!
     return nullptr;
   }
-  return outer->GetParentInternal();
+  return outer->GetInProcessParentInternal();
 }
 
 nsIPrincipal* nsGlobalWindowInner::GetTopLevelPrincipal() {
@@ -5609,7 +5611,7 @@ nsIPrincipal* nsGlobalWindowInner::GetTopLevelPrincipal() {
     return nullptr;
   }
 
-  nsPIDOMWindowOuter* topLevelOuterWindow = GetTopInternal();
+  nsPIDOMWindowOuter* topLevelOuterWindow = GetInProcessTopInternal();
   if (!topLevelOuterWindow) {
     return nullptr;
   }
@@ -5640,7 +5642,7 @@ nsIPrincipal* nsGlobalWindowInner::GetTopLevelStorageAreaPrincipal() {
     return nullptr;
   }
 
-  nsPIDOMWindowOuter* outerWindow = GetParentInternal();
+  nsPIDOMWindowOuter* outerWindow = GetInProcessParentInternal();
   if (!outerWindow) {
     // No outer window available!
     return nullptr;
diff --git a/dom/base/nsGlobalWindowInner.h b/dom/base/nsGlobalWindowInner.h
index 6d91ca561e22..84b85c9b655c 100644
--- a/dom/base/nsGlobalWindowInner.h
+++ b/dom/base/nsGlobalWindowInner.h
@@ -409,10 +409,10 @@ class nsGlobalWindowInner final : public mozilla::dom::EventTarget,
   void GetOwnPropertyNames(JSContext* aCx, JS::MutableHandleVector<jsid> aNames,
                            bool aEnumerableOnly, mozilla::ErrorResult& aRv);
 
-  nsPIDOMWindowOuter* GetScriptableTop() override;
-  inline nsGlobalWindowOuter* GetTopInternal();
+  nsPIDOMWindowOuter* GetInProcessScriptableTop() override;
+  inline nsGlobalWindowOuter* GetInProcessTopInternal();
 
-  inline nsGlobalWindowOuter* GetScriptableTopInternal();
+  inline nsGlobalWindowOuter* GetInProcessScriptableTopInternal();
 
   already_AddRefed<mozilla::dom::BrowsingContext> GetChildWindow(
       const nsAString& aName);
@@ -631,7 +631,7 @@ class nsGlobalWindowInner final : public mozilla::dom::EventTarget,
   void GetEvent(JSContext* aCx, JS::MutableHandle<JS::Value> aRetval);
   mozilla::dom::Nullable<mozilla::dom::WindowProxyHolder> GetParent(
       mozilla::ErrorResult& aError);
-  nsPIDOMWindowOuter* GetScriptableParent() override;
+  nsPIDOMWindowOuter* GetInProcessScriptableParent() override;
   mozilla::dom::Element* GetFrameElement(nsIPrincipal& aSubjectPrincipal,
                                          mozilla::ErrorResult& aError);
   mozilla::dom::Element* GetFrameElement() override;
@@ -1037,7 +1037,7 @@ class nsGlobalWindowInner final : public mozilla::dom::EventTarget,
   nsresult DefineArgumentsProperty(nsIArray* aArguments);
 
   // Get the parent, returns null if this is a toplevel window
-  nsPIDOMWindowOuter* GetParentInternal();
+  nsPIDOMWindowOuter* GetInProcessParentInternal();
 
  public:
   // popup tracking
@@ -1498,17 +1498,18 @@ inline nsIGlobalObject* nsGlobalWindowInner::GetOwnerGlobal() const {
   return const_cast<nsGlobalWindowInner*>(this);
 }
 
-inline nsGlobalWindowOuter* nsGlobalWindowInner::GetTopInternal() {
+inline nsGlobalWindowOuter* nsGlobalWindowInner::GetInProcessTopInternal() {
   nsGlobalWindowOuter* outer = GetOuterWindowInternal();
-  nsCOMPtr<nsPIDOMWindowOuter> top = outer ? outer->GetTop() : nullptr;
+  nsCOMPtr<nsPIDOMWindowOuter> top = outer ? outer->GetInProcessTop() : nullptr;
   if (top) {
     return nsGlobalWindowOuter::Cast(top);
   }
   return nullptr;
 }
 
-inline nsGlobalWindowOuter* nsGlobalWindowInner::GetScriptableTopInternal() {
-  nsPIDOMWindowOuter* top = GetScriptableTop();
+inline nsGlobalWindowOuter*
+nsGlobalWindowInner::GetInProcessScriptableTopInternal() {
+  nsPIDOMWindowOuter* top = GetInProcessScriptableTop();
   return nsGlobalWindowOuter::Cast(top);
 }
 
@@ -1534,7 +1535,7 @@ inline bool nsGlobalWindowInner::IsPopupSpamWindow() {
 }
 
 inline bool nsGlobalWindowInner::IsFrame() {
-  return GetParentInternal() != nullptr;
+  return GetInProcessParentInternal() != nullptr;
 }
 
 #endif /* nsGlobalWindowInner_h___ */
diff --git a/dom/base/nsGlobalWindowOuter.cpp b/dom/base/nsGlobalWindowOuter.cpp
index a27b97f120bd..29906deca653 100644
--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -1642,17 +1642,17 @@ bool nsGlobalWindowOuter::ComputeIsSecureContext(Document* aDocument,
 
   bool hadNonSecureContextCreator = false;
 
-  nsPIDOMWindowOuter* parentOuterWin = GetScriptableParent();
+  nsPIDOMWindowOuter* parentOuterWin = GetInProcessScriptableParent();
   MOZ_ASSERT(parentOuterWin, "How can we get here? No docShell somehow?");
   if (nsGlobalWindowOuter::Cast(parentOuterWin) != this) {
     // There may be a small chance that parentOuterWin has navigated in
     // the time that it took us to start loading this sub-document.  If that
     // were the case then parentOuterWin->GetCurrentInnerWindow() wouldn't
     // return the window for the document that is embedding us.  For this
-    // reason we only use the GetScriptableParent call above to check that we
-    // have a same-type parent, but actually get the inner window via the
-    // document that we know is embedding us.
-    Document* creatorDoc = aDocument->GetParentDocument();
+    // reason we only use the GetInProcessScriptableParent call above to check
+    // that we have a same-type parent, but actually get the inner window via
+    // the document that we know is embedding us.
+    Document* creatorDoc = aDocument->GetInProcessParentDocument();
     if (!creatorDoc) {
       return false;  // we must be tearing down
     }
@@ -1795,7 +1795,7 @@ static JS::RealmCreationOptions& SelectZone(
   }
 
   if (aNewInner->GetOuterWindow()) {
-    nsGlobalWindowOuter* top = aNewInner->GetTopInternal();
+    nsGlobalWindowOuter* top = aNewInner->GetInProcessTopInternal();
     if (top == aNewInner->GetOuterWindow()) {
       // We're a toplevel load.  Use a new zone.  This way, when we do
       // zone-based compartment sharing we won't share compartments
@@ -2405,13 +2405,14 @@ void nsGlobalWindowOuter::SetDocShell(nsDocShell* aDocShell) {
   mDocShell = aDocShell;
   mBrowsingContext = aDocShell->GetBrowsingContext();
 
-  nsCOMPtr<nsPIDOMWindowOuter> parentWindow = GetScriptableParentOrNull();
+  nsCOMPtr<nsPIDOMWindowOuter> parentWindow =
+      GetInProcessScriptableParentOrNull();
   MOZ_RELEASE_ASSERT(!parentWindow || !mTabGroup ||
                      mTabGroup ==
                          nsGlobalWindowOuter::Cast(parentWindow)->mTabGroup);
 
   mTopLevelOuterContentWindow =
-      !mIsChrome && GetScriptableTopInternal() == this;
+      !mIsChrome && GetInProcessScriptableTopInternal() == this;
 
   // Get our enclosing chrome shell and retrieve its global window impl, so
   // that we can do some forwarding to the chrome document.
@@ -2425,7 +2426,7 @@ void nsGlobalWindowOuter::SetDocShell(nsDocShell* aDocShell) {
     // window root object that will function as a chrome event
     // handler and receive all events that occur anywhere inside
     // our window.
-    nsCOMPtr<nsPIDOMWindowOuter> parentWindow = GetParent();
+    nsCOMPtr<nsPIDOMWindowOuter> parentWindow = GetInProcessParent();
     if (parentWindow.get() != this) {
       mChromeEventHandler = parentWindow->GetChromeEventHandler();
     } else {
@@ -2587,7 +2588,7 @@ void nsGlobalWindowOuter::UpdateParentTarget() {
   mMessageManager = nsContentUtils::TryGetBrowserChildGlobal(frameElement);
 
   if (!mMessageManager) {
-    nsGlobalWindowOuter* topWin = GetScriptableTopInternal();
+    nsGlobalWindowOuter* topWin = GetInProcessScriptableTopInternal();
     if (topWin) {
       frameElement = topWin->GetFrameElementInternal();
       mMessageManager = nsContentUtils::TryGetBrowserChildGlobal(frameElement);
@@ -2615,7 +2616,7 @@ void nsGlobalWindowOuter::GetEventTargetParent(EventChainPreVisitor& aVisitor) {
 }
 
 bool nsGlobalWindowOuter::ShouldPromptToBlockDialogs() {
-  nsGlobalWindowOuter* topWindowOuter = GetScriptableTopInternal();
+  nsGlobalWindowOuter* topWindowOuter = GetInProcessScriptableTopInternal();
   if (!topWindowOuter) {
     NS_ASSERTION(!mDocShell,
                  "ShouldPromptToBlockDialogs() called without a top window?");
@@ -2632,7 +2633,7 @@ bool nsGlobalWindowOuter::ShouldPromptToBlockDialogs() {
 }
 
 bool nsGlobalWindowOuter::AreDialogsEnabled() {
-  nsGlobalWindowOuter* topWindowOuter = GetScriptableTopInternal();
+  nsGlobalWindowOuter* topWindowOuter = GetInProcessScriptableTopInternal();
   if (!topWindowOuter) {
     NS_ERROR("AreDialogsEnabled() called without a top window?");
     return false;
@@ -2700,7 +2701,7 @@ bool nsGlobalWindowOuter::ConfirmDialogIfNeeded() {
 }
 
 void nsGlobalWindowOuter::DisableDialogs() {
-  nsGlobalWindowOuter* topWindowOuter = GetScriptableTopInternal();
+  nsGlobalWindowOuter* topWindowOuter = GetInProcessScriptableTopInternal();
   if (!topWindowOuter) {
     NS_ERROR("DisableDialogs() called without a top window?");
     return;
@@ -2715,7 +2716,7 @@ void nsGlobalWindowOuter::DisableDialogs() {
 }
 
 void nsGlobalWindowOuter::EnableDialogs() {
-  nsGlobalWindowOuter* topWindowOuter = GetScriptableTopInternal();
+  nsGlobalWindowOuter* topWindowOuter = GetInProcessScriptableTopInternal();
   if (!topWindowOuter) {
     NS_ERROR("EnableDialogs() called without a top window?");
     return;
@@ -2784,7 +2785,7 @@ nsIPrincipal* nsGlobalWindowOuter::GetPrincipal() {
   // a document into the window.
 
   nsCOMPtr<nsIScriptObjectPrincipal> objPrincipal =
-      do_QueryInterface(GetParentInternal());
+      do_QueryInterface(GetInProcessParentInternal());
 
   if (objPrincipal) {
     return objPrincipal->GetPrincipal();
@@ -2807,7 +2808,7 @@ nsIPrincipal* nsGlobalWindowOuter::GetEffectiveStoragePrincipal() {
   // the parent window for the storage principal.
 
   nsCOMPtr<nsIScriptObjectPrincipal> objPrincipal =
-      do_QueryInterface(GetParentInternal());
+      do_QueryInterface(GetInProcessParentInternal());
 
   if (objPrincipal) {
     return objPrincipal->GetEffectiveStoragePrincipal();
@@ -2951,7 +2952,7 @@ void nsPIDOMWindowOuter::SetServiceWorkersTestingEnabled(bool aEnabled) {
   // ok if devtools clears the flag on clean up of nested windows, though.
   // It will have no affect.
 #ifdef DEBUG
-  nsCOMPtr<nsPIDOMWindowOuter> topWindow = GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topWindow = GetInProcessScriptableTop();
   MOZ_ASSERT_IF(aEnabled, this == topWindow);
 #endif
   mServiceWorkersTestingEnabled = aEnabled;
@@ -2960,7 +2961,7 @@ void nsPIDOMWindowOuter::SetServiceWorkersTestingEnabled(bool aEnabled) {
 bool nsPIDOMWindowOuter::GetServiceWorkersTestingEnabled() {
   // Automatically get this setting from the top level window so that nested
   // iframes get the correct devtools setting.
-  nsCOMPtr<nsPIDOMWindowOuter> topWindow = GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topWindow = GetInProcessScriptableTop();
   if (!topWindow) {
     return false;
   }
@@ -2973,13 +2974,13 @@ Nullable<WindowProxyHolder> nsGlobalWindowOuter::GetParentOuter() {
 }
 
 /**
- * GetScriptableParent is called when script reads window.parent.
+ * GetInProcessScriptableParent is called when script reads window.parent.
  *
- * In contrast to GetRealParent, GetScriptableParent respects <iframe
+ * In contrast to GetRealParent, GetInProcessScriptableParent respects <iframe
  * mozbrowser> boundaries, so if |this| is contained by an <iframe
  * mozbrowser>, we will return |this| as its own parent.
  */
-nsPIDOMWindowOuter* nsGlobalWindowOuter::GetScriptableParent() {
+nsPIDOMWindowOuter* nsGlobalWindowOuter::GetInProcessScriptableParent() {
   if (!mDocShell) {
     return nullptr;
   }
@@ -2988,16 +2989,16 @@ nsPIDOMWindowOuter* nsGlobalWindowOuter::GetScriptableParent() {
     return this;
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> parent = GetParent();
+  nsCOMPtr<nsPIDOMWindowOuter> parent = GetInProcessParent();
   return parent;
 }
 
 /**
- * Behavies identically to GetScriptableParent extept that it returns null
- * if GetScriptableParent would return this window.
+ * Behavies identically to GetInProcessScriptableParent extept that it returns
+ * null if GetInProcessScriptableParent would return this window.
  */
-nsPIDOMWindowOuter* nsGlobalWindowOuter::GetScriptableParentOrNull() {
-  nsPIDOMWindowOuter* parent = GetScriptableParent();
+nsPIDOMWindowOuter* nsGlobalWindowOuter::GetInProcessScriptableParentOrNull() {
+  nsPIDOMWindowOuter* parent = GetInProcessScriptableParent();
   return (nsGlobalWindowOuter::Cast(parent) == this) ? nullptr : parent;
 }
 
@@ -3005,7 +3006,7 @@ nsPIDOMWindowOuter* nsGlobalWindowOuter::GetScriptableParentOrNull() {
  * nsPIDOMWindow::GetParent (when called from C++) is just a wrapper around
  * GetRealParent.
  */
-already_AddRefed<nsPIDOMWindowOuter> nsGlobalWindowOuter::GetParent() {
+already_AddRefed<nsPIDOMWindowOuter> nsGlobalWindowOuter::GetInProcessParent() {
   if (!mDocShell) {
     return nullptr;
   }
@@ -3041,9 +3042,9 @@ static nsresult GetTopImpl(nsGlobalWindowOuter* aWin, nsIURI* aURIBeingLoaded,
     prevParent = parent;
 
     if (aScriptable) {
-      parent = parent->GetScriptableParent();
+      parent = parent->GetInProcessScriptableParent();
     } else {
-      parent = parent->GetParent();
+      parent = parent->GetInProcessParent();
     }
 
     if (aExcludingExtensionAccessibleContentFrames) {
@@ -3093,13 +3094,14 @@ static nsresult GetTopImpl(nsGlobalWindowOuter* aWin, nsIURI* aURIBeingLoaded,
 }
 
 /**
- * GetScriptableTop is called when script reads window.top.
+ * GetInProcessScriptableTop is called when script reads window.top.
  *
- * In contrast to GetRealTop, GetScriptableTop respects <iframe mozbrowser>
- * boundaries.  If we encounter a window owned by an <iframe mozbrowser> while
- * walking up the window hierarchy, we'll stop and return that window.
+ * In contrast to GetRealTop, GetInProcessScriptableTop respects <iframe
+ * mozbrowser> boundaries.  If we encounter a window owned by an <iframe
+ * mozbrowser> while walking up the window hierarchy, we'll stop and return that
+ * window.
  */
-nsPIDOMWindowOuter* nsGlobalWindowOuter::GetScriptableTop() {
+nsPIDOMWindowOuter* nsGlobalWindowOuter::GetInProcessScriptableTop() {
   nsCOMPtr<nsPIDOMWindowOuter> window;
   GetTopImpl(this, /* aURIBeingLoaded = */ nullptr, getter_AddRefs(window),
              /* aScriptable = */ true,
@@ -3107,7 +3109,7 @@ nsPIDOMWindowOuter* nsGlobalWindowOuter::GetScriptableTop() {
   return window.get();
 }
 
-already_AddRefed<nsPIDOMWindowOuter> nsGlobalWindowOuter::GetTop() {
+already_AddRefed<nsPIDOMWindowOuter> nsGlobalWindowOuter::GetInProcessTop() {
   nsCOMPtr<nsPIDOMWindowOuter> window;
   GetTopImpl(this, /* aURIBeingLoaded = */ nullptr, getter_AddRefs(window),
              /* aScriptable = */ false,
@@ -3161,7 +3163,7 @@ already_AddRefed<nsPIDOMWindowOuter> nsGlobalWindowOuter::GetContentInternal(
   // If we're contained in <iframe mozbrowser>, then GetContent is the same as
   // window.top.
   if (mDocShell && mDocShell->GetIsInMozBrowser()) {
-    nsCOMPtr<nsPIDOMWindowOuter> domWindow(GetScriptableTop());
+    nsCOMPtr<nsPIDOMWindowOuter> domWindow(GetInProcessScriptableTop());
     return domWindow.forget();
   }
 
@@ -3181,7 +3183,8 @@ already_AddRefed<nsPIDOMWindowOuter> nsGlobalWindowOuter::GetContentInternal(
       baseWin->GetVisibility(&visible);
 
       if (!visible) {
-        mDocShell->GetSameTypeRootTreeItem(getter_AddRefs(primaryContent));
+        mDocShell->GetInProcessSameTypeRootTreeItem(
+            getter_AddRefs(primaryContent));
       }
     }
   }
@@ -4464,7 +4467,8 @@ bool nsGlobalWindowOuter::SetWidgetFullscreen(FullscreenReason aReason,
                                               bool aIsFullscreen,
                                               nsIWidget* aWidget,
                                               nsIScreen* aScreen) {
-  MOZ_ASSERT(this == GetTopInternal(), "Only topmost window should call this");
+  MOZ_ASSERT(this == GetInProcessTopInternal(),
+             "Only topmost window should call this");
   MOZ_ASSERT(!GetFrameElementInternal(), "Content window should not call this");
   MOZ_ASSERT(XRE_GetProcessType() == GeckoProcessType_Default);
 
@@ -4946,7 +4950,7 @@ void nsGlobalWindowOuter::FocusOuter() {
   // about:blank loaded.  We don't want to focus our widget in that case.
   // XXXbz should we really be checking for IsInitialDocument() instead?
   nsCOMPtr<nsIDocShellTreeItem> parentDsti;
-  mDocShell->GetParent(getter_AddRefs(parentDsti));
+  mDocShell->GetInProcessParent(getter_AddRefs(parentDsti));
 
   // set the parent's current focus to the frame containing this window.
   nsCOMPtr<nsPIDOMWindowOuter> parent =
@@ -5620,7 +5624,7 @@ bool nsGlobalWindowOuter::PopupWhitelisted() {
     return true;
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> parent = GetParent();
+  nsCOMPtr<nsPIDOMWindowOuter> parent = GetInProcessParent();
   if (parent == this) {
     return false;
   }
@@ -5687,7 +5691,7 @@ void nsGlobalWindowOuter::FireAbuseEvents(
     const nsAString& aPopupWindowFeatures) {
   // fetch the URI of the window requesting the opened window
 
-  nsCOMPtr<nsPIDOMWindowOuter> window = GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> window = GetInProcessTop();
   if (!window) {
     return;
   }
@@ -6372,9 +6376,9 @@ void nsGlobalWindowOuter::ReallyCloseWindow() {
 }
 
 void nsGlobalWindowOuter::EnterModalState() {
-  // GetScriptableTop, not GetTop, so that EnterModalState works properly with
-  // <iframe mozbrowser>.
-  nsGlobalWindowOuter* topWin = GetScriptableTopInternal();
+  // GetInProcessScriptableTop, not GetInProcessTop, so that EnterModalState
+  // works properly with <iframe mozbrowser>.
+  nsGlobalWindowOuter* topWin = GetInProcessScriptableTopInternal();
 
   if (!topWin) {
     NS_ERROR("Uh, EnterModalState() called w/o a reachable top window?");
@@ -6437,7 +6441,7 @@ void nsGlobalWindowOuter::EnterModalState() {
 }
 
 void nsGlobalWindowOuter::LeaveModalState() {
-  nsGlobalWindowOuter* topWin = GetScriptableTopInternal();
+  nsGlobalWindowOuter* topWin = GetInProcessScriptableTopInternal();
 
   if (!topWin) {
     NS_ERROR("Uh, LeaveModalState() called w/o a reachable top window?");
@@ -6479,7 +6483,7 @@ void nsGlobalWindowOuter::LeaveModalState() {
 }
 
 bool nsGlobalWindowOuter::IsInModalState() {
-  nsGlobalWindowOuter* topWin = GetScriptableTopInternal();
+  nsGlobalWindowOuter* topWin = GetInProcessScriptableTopInternal();
 
   if (!topWin) {
     // IsInModalState() getting called w/o a reachable top window is a bit
@@ -6718,7 +6722,7 @@ EventListenerManager* nsGlobalWindowOuter::GetExistingListenerManager() const {
 //*****************************************************************************
 
 nsPIDOMWindowOuter* nsGlobalWindowOuter::GetPrivateParent() {
-  nsCOMPtr<nsPIDOMWindowOuter> parent = GetParent();
+  nsCOMPtr<nsPIDOMWindowOuter> parent = GetInProcessParent();
 
   if (this == parent) {
     nsCOMPtr<nsIContent> chromeElement(do_QueryInterface(mChromeEventHandler));
@@ -6735,7 +6739,7 @@ nsPIDOMWindowOuter* nsGlobalWindowOuter::GetPrivateParent() {
 }
 
 nsPIDOMWindowOuter* nsGlobalWindowOuter::GetPrivateRoot() {
-  nsCOMPtr<nsPIDOMWindowOuter> top = GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> top = GetInProcessTop();
 
   nsCOMPtr<nsIContent> chromeElement(do_QueryInterface(mChromeEventHandler));
   if (chromeElement) {
@@ -6743,7 +6747,7 @@ nsPIDOMWindowOuter* nsGlobalWindowOuter::GetPrivateRoot() {
     if (doc) {
       nsCOMPtr<nsPIDOMWindowOuter> parent = doc->GetWindow();
       if (parent) {
-        top = parent->GetTop();
+        top = parent->GetInProcessTop();
       }
     }
   }
@@ -7080,8 +7084,8 @@ nsresult nsGlobalWindowOuter::FireDelayedDOMEvents() {
 // nsGlobalWindowOuter: Window Control Functions
 //*****************************************************************************
 
-nsPIDOMWindowOuter* nsGlobalWindowOuter::GetParentInternal() {
-  nsCOMPtr<nsPIDOMWindowOuter> parent = GetParent();
+nsPIDOMWindowOuter* nsGlobalWindowOuter::GetInProcessParentInternal() {
+  nsCOMPtr<nsPIDOMWindowOuter> parent = GetInProcessParent();
 
   if (parent && parent != this) {
     return parent;
@@ -7444,7 +7448,7 @@ void nsGlobalWindowOuter::EnsureSizeAndPositionUpToDate() {
   // through the document chain rather than the window chain to not flush on
   // detached iframes, see bug 1545516.
   if (mDoc && mDoc->StyleOrLayoutObservablyDependsOnParentDocumentLayout()) {
-    RefPtr<Document> parent = mDoc->GetParentDocument();
+    RefPtr<Document> parent = mDoc->GetInProcessParentDocument();
     parent->FlushPendingNotifications(FlushType::Layout);
   }
 }
@@ -7723,7 +7727,7 @@ mozilla::dom::TabGroup* nsGlobalWindowOuter::TabGroupOuter() {
     // which we want to return false.
     nsCOMPtr<nsPIDOMWindowOuter> piOpener = do_QueryReferent(mOpener);
     nsPIDOMWindowOuter* opener = GetSanitizedOpener(piOpener);
-    nsPIDOMWindowOuter* parent = GetScriptableParentOrNull();
+    nsPIDOMWindowOuter* parent = GetInProcessScriptableParentOrNull();
     MOZ_ASSERT(!parent || !opener,
                "Only one of parent and opener may be provided");
 
@@ -7758,7 +7762,7 @@ mozilla::dom::TabGroup* nsGlobalWindowOuter::TabGroupOuter() {
       MOZ_ASSERT(mTabGroup == TabGroup::GetChromeTabGroup());
     } else {
       // Sanity check that our tabgroup matches our opener or parent.
-      RefPtr<nsPIDOMWindowOuter> parent = GetScriptableParentOrNull();
+      RefPtr<nsPIDOMWindowOuter> parent = GetInProcessScriptableParentOrNull();
       MOZ_ASSERT_IF(parent, parent->TabGroup() == mTabGroup);
       nsCOMPtr<nsPIDOMWindowOuter> piOpener = do_QueryReferent(mOpener);
       nsPIDOMWindowOuter* opener = GetSanitizedOpener(piOpener);
@@ -7805,7 +7809,8 @@ nsGlobalWindowOuter::TemporarilyDisableDialogs::TemporarilyDisableDialogs(
   MOZ_GUARD_OBJECT_NOTIFIER_INIT;
 
   MOZ_ASSERT(aWindow);
-  nsGlobalWindowOuter* topWindowOuter = aWindow->GetScriptableTopInternal();
+  nsGlobalWindowOuter* topWindowOuter =
+      aWindow->GetInProcessScriptableTopInternal();
   if (!topWindowOuter) {
     NS_ERROR(
         "nsGlobalWindowOuter::TemporarilyDisableDialogs used without a top "
diff --git a/dom/base/nsGlobalWindowOuter.h b/dom/base/nsGlobalWindowOuter.h
index 296a09c32428..18b82b8c521b 100644
--- a/dom/base/nsGlobalWindowOuter.h
+++ b/dom/base/nsGlobalWindowOuter.h
@@ -359,17 +359,17 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
   mozilla::dom::Nullable<mozilla::dom::WindowProxyHolder> IndexedGetterOuter(
       uint32_t aIndex);
 
-  already_AddRefed<nsPIDOMWindowOuter> GetTop() override;
-  // Similar to GetTop() except that it stops at content frames that an
-  // extension has permission to access.  This is used by the third-party util
-  // service in order to determine the top window for a channel which is used
-  // in third-partiness checks.
+  already_AddRefed<nsPIDOMWindowOuter> GetInProcessTop() override;
+  // Similar to GetInProcessTop() except that it stops at content frames that
+  // an extension has permission to access.  This is used by the third-party
+  // util service in order to determine the top window for a channel which is
+  // used in third-partiness checks.
   already_AddRefed<nsPIDOMWindowOuter>
   GetTopExcludingExtensionAccessibleContentFrames(nsIURI* aURIBeingLoaded);
-  nsPIDOMWindowOuter* GetScriptableTop() override;
-  inline nsGlobalWindowOuter* GetTopInternal();
+  nsPIDOMWindowOuter* GetInProcessScriptableTop() override;
+  inline nsGlobalWindowOuter* GetInProcessTopInternal();
 
-  inline nsGlobalWindowOuter* GetScriptableTopInternal();
+  inline nsGlobalWindowOuter* GetInProcessScriptableTopInternal();
 
   already_AddRefed<mozilla::dom::BrowsingContext> GetChildWindow(
       const nsAString& aName);
@@ -555,9 +555,9 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
 
   already_AddRefed<nsPIDOMWindowOuter> GetOpener() override;
   mozilla::dom::Nullable<mozilla::dom::WindowProxyHolder> GetParentOuter();
-  already_AddRefed<nsPIDOMWindowOuter> GetParent() override;
-  nsPIDOMWindowOuter* GetScriptableParent() override;
-  nsPIDOMWindowOuter* GetScriptableParentOrNull() override;
+  already_AddRefed<nsPIDOMWindowOuter> GetInProcessParent() override;
+  nsPIDOMWindowOuter* GetInProcessScriptableParent() override;
+  nsPIDOMWindowOuter* GetInProcessScriptableParentOrNull() override;
   mozilla::dom::Element* GetFrameElementOuter(nsIPrincipal& aSubjectPrincipal);
   mozilla::dom::Element* GetFrameElement() override;
   mozilla::dom::Nullable<mozilla::dom::WindowProxyHolder> OpenOuter(
@@ -747,7 +747,7 @@ class nsGlobalWindowOuter final : public mozilla::dom::EventTarget,
   static nsGlobalWindowInner* CallerInnerWindow(JSContext* aCx);
 
   // Get the parent, returns null if this is a toplevel window
-  nsPIDOMWindowOuter* GetParentInternal();
+  nsPIDOMWindowOuter* GetInProcessParentInternal();
 
  public:
   // popup tracking
@@ -1176,16 +1176,17 @@ inline nsIGlobalObject* nsGlobalWindowOuter::GetOwnerGlobal() const {
   return GetCurrentInnerWindowInternal();
 }
 
-inline nsGlobalWindowOuter* nsGlobalWindowOuter::GetTopInternal() {
-  nsCOMPtr<nsPIDOMWindowOuter> top = GetTop();
+inline nsGlobalWindowOuter* nsGlobalWindowOuter::GetInProcessTopInternal() {
+  nsCOMPtr<nsPIDOMWindowOuter> top = GetInProcessTop();
   if (top) {
     return nsGlobalWindowOuter::Cast(top);
   }
   return nullptr;
 }
 
-inline nsGlobalWindowOuter* nsGlobalWindowOuter::GetScriptableTopInternal() {
-  nsPIDOMWindowOuter* top = GetScriptableTop();
+inline nsGlobalWindowOuter*
+nsGlobalWindowOuter::GetInProcessScriptableTopInternal() {
+  nsPIDOMWindowOuter* top = GetInProcessScriptableTop();
   return nsGlobalWindowOuter::Cast(top);
 }
 
@@ -1203,14 +1204,14 @@ inline nsGlobalWindowInner* nsGlobalWindowOuter::EnsureInnerWindowInternal() {
 }
 
 inline bool nsGlobalWindowOuter::IsTopLevelWindow() {
-  nsPIDOMWindowOuter* parentWindow = GetScriptableTop();
+  nsPIDOMWindowOuter* parentWindow = GetInProcessScriptableTop();
   return parentWindow == this;
 }
 
 inline bool nsGlobalWindowOuter::IsPopupSpamWindow() { return mIsPopupSpam; }
 
 inline bool nsGlobalWindowOuter::IsFrame() {
-  return GetParentInternal() != nullptr;
+  return GetInProcessParentInternal() != nullptr;
 }
 
 inline void nsGlobalWindowOuter::MaybeClearInnerWindow(
diff --git a/dom/base/nsHistory.cpp b/dom/base/nsHistory.cpp
index 7d573e7ad696..82295b6479c0 100644
--- a/dom/base/nsHistory.cpp
+++ b/dom/base/nsHistory.cpp
@@ -296,7 +296,7 @@ already_AddRefed<ChildSHistory> nsHistory::GetSessionHistory() const {
 
   // Get the root DocShell from it
   nsCOMPtr<nsIDocShellTreeItem> root;
-  docShell->GetSameTypeRootTreeItem(getter_AddRefs(root));
+  docShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   nsCOMPtr<nsIWebNavigation> webNav(do_QueryInterface(root));
   NS_ENSURE_TRUE(webNav, nullptr);
 
diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index b2ba2d835134..4c5c58cd3d24 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -1954,7 +1954,7 @@ void nsJSContext::MaybeRunNextCollectorSlice(nsIDocShell* aDocShell,
   }
 
   nsCOMPtr<nsIDocShellTreeItem> root;
-  aDocShell->GetSameTypeRootTreeItem(getter_AddRefs(root));
+  aDocShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   if (root == aDocShell) {
     // We don't want to run collectors when loading the top level page.
     return;
diff --git a/dom/base/nsObjectLoadingContent.cpp b/dom/base/nsObjectLoadingContent.cpp
index a66e22e7bdae..db5e693ed236 100644
--- a/dom/base/nsObjectLoadingContent.cpp
+++ b/dom/base/nsObjectLoadingContent.cpp
@@ -3051,7 +3051,7 @@ bool nsObjectLoadingContent::ShouldPlay(FallbackType& aReason) {
   if (!window) {
     return false;
   }
-  nsCOMPtr<nsPIDOMWindowOuter> topWindow = window->GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topWindow = window->GetInProcessTop();
   NS_ENSURE_TRUE(topWindow, false);
   nsCOMPtr<Document> topDoc = topWindow->GetDoc();
   NS_ENSURE_TRUE(topDoc, false);
diff --git a/dom/base/nsPIDOMWindow.h b/dom/base/nsPIDOMWindow.h
index d454e56261a9..fde24ef06a01 100644
--- a/dom/base/nsPIDOMWindow.h
+++ b/dom/base/nsPIDOMWindow.h
@@ -348,8 +348,8 @@ class nsPIDOMWindowInner : public mozIDOMWindow {
   virtual mozilla::dom::CustomElementRegistry* CustomElements() = 0;
 
   // XXX: This is called on inner windows
-  virtual nsPIDOMWindowOuter* GetScriptableTop() = 0;
-  virtual nsPIDOMWindowOuter* GetScriptableParent() = 0;
+  virtual nsPIDOMWindowOuter* GetInProcessScriptableTop() = 0;
+  virtual nsPIDOMWindowOuter* GetInProcessScriptableParent() = 0;
   virtual already_AddRefed<nsPIWindowRoot> GetTopWindowRoot() = 0;
 
   mozilla::dom::EventTarget* GetChromeEventHandler() const {
@@ -778,24 +778,25 @@ class nsPIDOMWindowOuter : public mozIDOMWindowProxy {
    * This function does not cross chrome-content boundaries, so if this
    * window's parent is of a different type, |top| will return this window.
    *
-   * When script reads the top property, we run GetScriptableTop, which
-   * will not cross an <iframe mozbrowser> boundary.
+   * When script reads the top property, we run GetInProcessScriptableTop,
+   * which will not cross an <iframe mozbrowser> boundary.
    *
    * In contrast, C++ calls to GetTop are forwarded to GetRealTop, which
    * ignores <iframe mozbrowser> boundaries.
    */
 
-  virtual already_AddRefed<nsPIDOMWindowOuter> GetTop() = 0;  // Outer only
-  virtual already_AddRefed<nsPIDOMWindowOuter> GetParent() = 0;
-  virtual nsPIDOMWindowOuter* GetScriptableTop() = 0;
-  virtual nsPIDOMWindowOuter* GetScriptableParent() = 0;
+  virtual already_AddRefed<nsPIDOMWindowOuter>
+  GetInProcessTop() = 0;  // Outer only
+  virtual already_AddRefed<nsPIDOMWindowOuter> GetInProcessParent() = 0;
+  virtual nsPIDOMWindowOuter* GetInProcessScriptableTop() = 0;
+  virtual nsPIDOMWindowOuter* GetInProcessScriptableParent() = 0;
   virtual already_AddRefed<nsPIWindowRoot> GetTopWindowRoot() = 0;
 
   /**
-   * Behaves identically to GetScriptableParent except that it returns null
-   * if GetScriptableParent would return this window.
+   * Behaves identically to GetInProcessScriptableParent except that it
+   * returns null if GetInProcessScriptableParent would return this window.
    */
-  virtual nsPIDOMWindowOuter* GetScriptableParentOrNull() = 0;
+  virtual nsPIDOMWindowOuter* GetInProcessScriptableParentOrNull() = 0;
 
   virtual bool IsTopLevelWindowActive() = 0;
 
diff --git a/dom/base/nsScreen.cpp b/dom/base/nsScreen.cpp
index 4261827470ea..465c4a06dfd8 100644
--- a/dom/base/nsScreen.cpp
+++ b/dom/base/nsScreen.cpp
@@ -204,7 +204,7 @@ static void UpdateDocShellOrientationLock(nsPIDOMWindowInner* aWindow,
   }
 
   nsCOMPtr<nsIDocShellTreeItem> root;
-  docShell->GetSameTypeRootTreeItem(getter_AddRefs(root));
+  docShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
   nsCOMPtr<nsIDocShell> rootShell(do_QueryInterface(root));
   if (!rootShell) {
     return;
diff --git a/dom/base/nsWindowMemoryReporter.cpp b/dom/base/nsWindowMemoryReporter.cpp
index 33521abd2c4d..364835aa3c09 100644
--- a/dom/base/nsWindowMemoryReporter.cpp
+++ b/dom/base/nsWindowMemoryReporter.cpp
@@ -224,14 +224,15 @@ static void CollectWindowReports(nsGlobalWindowInner* aWindow,
                                  nsISupports* aData, bool aAnonymize) {
   nsAutoCString windowPath("explicit/");
 
-  // Avoid calling aWindow->GetTop() if there's no outer window.  It will work
-  // just fine, but will spew a lot of warnings.
+  // Avoid calling aWindow->GetInProcessTop() if there's no outer window.  It
+  // will work just fine, but will spew a lot of warnings.
   nsGlobalWindowOuter* top = nullptr;
   nsCOMPtr<nsIURI> location;
   if (aWindow->GetOuterWindow()) {
     // Our window should have a null top iff it has a null docshell.
-    MOZ_ASSERT(!!aWindow->GetTopInternal() == !!aWindow->GetDocShell());
-    top = aWindow->GetTopInternal();
+    MOZ_ASSERT(!!aWindow->GetInProcessTopInternal() ==
+               !!aWindow->GetDocShell());
+    top = aWindow->GetInProcessTopInternal();
     if (top) {
       location = GetWindowURI(top);
     }
@@ -816,10 +817,10 @@ void nsWindowMemoryReporter::CheckForGhostWindows(
 
   // Populate nonDetachedTabGroups.
   for (auto iter = windowsById->Iter(); !iter.Done(); iter.Next()) {
-    // Null outer window implies null top, but calling GetTop() when there's no
-    // outer window causes us to spew debug warnings.
+    // Null outer window implies null top, but calling GetInProcessTop() when
+    // there's no outer window causes us to spew debug warnings.
     nsGlobalWindowInner* window = iter.UserData();
-    if (!window->GetOuterWindow() || !window->GetTopInternal()) {
+    if (!window->GetOuterWindow() || !window->GetInProcessTopInternal()) {
       // This window is detached, so we don't care about its tab group.
       continue;
     }
@@ -844,12 +845,12 @@ void nsWindowMemoryReporter::CheckForGhostWindows(
 
     nsPIDOMWindowInner* window = nsPIDOMWindowInner::From(iwindow);
 
-    // Avoid calling GetTop() if we have no outer window.  Nothing will break if
-    // we do, but it will spew debug output, which can cause our test logs to
-    // overflow.
+    // Avoid calling GetInProcessTop() if we have no outer window.  Nothing
+    // will break if we do, but it will spew debug output, which can cause our
+    // test logs to overflow.
     nsCOMPtr<nsPIDOMWindowOuter> top;
     if (window->GetOuterWindow()) {
-      top = window->GetOuterWindow()->GetTop();
+      top = window->GetOuterWindow()->GetInProcessTop();
     }
 
     if (top) {
diff --git a/dom/browser-element/BrowserElementParent.cpp b/dom/browser-element/BrowserElementParent.cpp
index 46d067e4990c..7b0764dad6e8 100644
--- a/dom/browser-element/BrowserElementParent.cpp
+++ b/dom/browser-element/BrowserElementParent.cpp
@@ -227,11 +227,11 @@ BrowserElementParent::OpenWindowInProcess(BrowsingContext* aOpenerWindow,
   // called window.open.  (Indeed, in the OOP case, the inner <iframe> lives
   // out-of-process, so we couldn't touch it if we tried.)
   //
-  // GetScriptableTop gets us the <iframe mozbrowser>'s window; we'll use its
-  // frame element, rather than aOpenerWindow's frame element, as our "opener
-  // frame element" below.
+  // GetInProcessScriptableTop gets us the <iframe mozbrowser>'s window; we'll
+  // use its frame element, rather than aOpenerWindow's frame element, as our
+  // "opener frame element" below.
   nsCOMPtr<nsPIDOMWindowOuter> win =
-      aOpenerWindow->GetDOMWindow()->GetScriptableTop();
+      aOpenerWindow->GetDOMWindow()->GetInProcessScriptableTop();
 
   nsCOMPtr<Element> openerFrameElement = win->GetFrameElementInternal();
   NS_ENSURE_TRUE(openerFrameElement, BrowserElementParent::OPEN_WINDOW_IGNORED);
diff --git a/dom/events/EventStateManager.cpp b/dom/events/EventStateManager.cpp
index ff2e216cf540..7bc0eaa52855 100644
--- a/dom/events/EventStateManager.cpp
+++ b/dom/events/EventStateManager.cpp
@@ -460,8 +460,9 @@ nsresult EventStateManager::PreHandleEvent(nsPresContext* aPresContext,
       Document* doc = node->OwnerDoc();
       while (doc) {
         doc->SetUserHasInteracted();
-        doc = nsContentUtils::IsChildOfSameType(doc) ? doc->GetParentDocument()
-                                                     : nullptr;
+        doc = nsContentUtils::IsChildOfSameType(doc)
+                  ? doc->GetInProcessParentDocument()
+                  : nullptr;
       }
     }
   }
@@ -1140,11 +1141,11 @@ bool EventStateManager::WalkESMTreeToHandleAccessKey(
   }
 
   int32_t childCount;
-  docShell->GetChildCount(&childCount);
+  docShell->GetInProcessChildCount(&childCount);
   for (int32_t counter = 0; counter < childCount; counter++) {
     // Not processing the child which bubbles up the handling
     nsCOMPtr<nsIDocShellTreeItem> subShellItem;
-    docShell->GetChildAt(counter, getter_AddRefs(subShellItem));
+    docShell->GetInProcessChildAt(counter, getter_AddRefs(subShellItem));
     if (aAccessKeyState == eAccessKeyProcessingUp &&
         subShellItem == aBubbledFrom) {
       continue;
@@ -1180,7 +1181,7 @@ bool EventStateManager::WalkESMTreeToHandleAccessKey(
   // bubble up the process to the parent docshell if necessary
   if (eAccessKeyProcessingDown != aAccessKeyState) {
     nsCOMPtr<nsIDocShellTreeItem> parentShellItem;
-    docShell->GetParent(getter_AddRefs(parentShellItem));
+    docShell->GetInProcessParent(getter_AddRefs(parentShellItem));
     nsCOMPtr<nsIDocShell> parentDS = do_QueryInterface(parentShellItem);
     if (parentDS) {
       // Guarantee parentPresShell lifetime while we're handling access key
@@ -3253,8 +3254,8 @@ nsresult EventStateManager::PostHandleEvent(nsPresContext* aPresContext,
               !nsContentUtils::IsChromeDoc(mDocument)) {
             nsCOMPtr<nsPIDOMWindowOuter> currentTop;
             nsCOMPtr<nsPIDOMWindowOuter> newTop;
-            currentTop = currentWindow->GetTop();
-            newTop = mDocument->GetWindow()->GetTop();
+            currentTop = currentWindow->GetInProcessTop();
+            newTop = mDocument->GetWindow()->GetInProcessTop();
             nsCOMPtr<Document> currentDoc = currentWindow->GetExtantDoc();
             if (nsContentUtils::IsChromeDoc(currentDoc) ||
                 (currentTop && newTop && currentTop != newTop)) {
@@ -4389,7 +4390,7 @@ void EventStateManager::NotifyMouseOver(WidgetMouseEvent* aMouseEvent,
   // document's ESM state to indicate that the mouse is over the
   // content associated with our subdocument.
   EnsureDocument(mPresContext);
-  if (Document* parentDoc = mDocument->GetParentDocument()) {
+  if (Document* parentDoc = mDocument->GetInProcessParentDocument()) {
     if (nsCOMPtr<nsIContent> docContent =
             parentDoc->FindContentForSubDocument(mDocument)) {
       if (PresShell* parentPresShell = parentDoc->GetPresShell()) {
diff --git a/dom/html/HTMLCanvasElement.cpp b/dom/html/HTMLCanvasElement.cpp
index 3ff4ab4914ae..5eade5c8b0ec 100644
--- a/dom/html/HTMLCanvasElement.cpp
+++ b/dom/html/HTMLCanvasElement.cpp
@@ -1207,8 +1207,8 @@ nsresult HTMLCanvasElement::RegisterFrameCaptureListener(
       return NS_ERROR_FAILURE;
     }
 
-    while (doc->GetParentDocument()) {
-      doc = doc->GetParentDocument();
+    while (doc->GetInProcessParentDocument()) {
+      doc = doc->GetInProcessParentDocument();
     }
 
     nsPresContext* context = doc->GetPresContext();
diff --git a/dom/html/HTMLFormElement.cpp b/dom/html/HTMLFormElement.cpp
index 0e7f0a1a8712..88b9bfe94162 100644
--- a/dom/html/HTMLFormElement.cpp
+++ b/dom/html/HTMLFormElement.cpp
@@ -739,7 +739,7 @@ nsresult HTMLFormElement::DoSecureToInsecureSubmitCheck(nsIURI* aActionURL,
   // Only ask the user about posting from a secure URI to an insecure URI if
   // this element is in the root document. When this is not the case, the mixed
   // content blocker will take care of security for us.
-  Document* parent = OwnerDoc()->GetParentDocument();
+  Document* parent = OwnerDoc()->GetInProcessParentDocument();
   bool isRootDocument = (!parent || nsContentUtils::IsChromeDoc(parent));
   if (!isRootDocument) {
     return NS_OK;
diff --git a/dom/html/HTMLMediaElement.cpp b/dom/html/HTMLMediaElement.cpp
index f91905012974..5c92c53c23c1 100644
--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -6691,7 +6691,8 @@ already_AddRefed<nsIPrincipal> HTMLMediaElement::GetTopLevelPrincipal() {
     return nullptr;
   }
   // XXXkhuey better hope we always have an outer ...
-  nsCOMPtr<nsPIDOMWindowOuter> top = window->GetOuterWindow()->GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> top =
+      window->GetOuterWindow()->GetInProcessTop();
   if (!top) {
     return nullptr;
   }
diff --git a/dom/html/nsHTMLDocument.cpp b/dom/html/nsHTMLDocument.cpp
index 974438f2433d..93d8ed321f85 100644
--- a/dom/html/nsHTMLDocument.cpp
+++ b/dom/html/nsHTMLDocument.cpp
@@ -537,7 +537,7 @@ nsresult nsHTMLDocument::StartDocumentLoad(const char* aCommand,
   // and parentContentViewer
   nsCOMPtr<nsIDocShellTreeItem> parentAsItem;
   if (docShell) {
-    docShell->GetSameTypeParent(getter_AddRefs(parentAsItem));
+    docShell->GetInProcessSameTypeParent(getter_AddRefs(parentAsItem));
   }
 
   nsCOMPtr<nsIDocShell> parent(do_QueryInterface(parentAsItem));
diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index e50008f2fc14..ab4b1246a390 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -1015,7 +1015,7 @@ nsresult ContentChild::ProvideWindowCommon(
   nsCOMPtr<nsPIDOMWindowInner> parentTopInnerWindow;
   if (aParent) {
     nsCOMPtr<nsPIDOMWindowOuter> parentTopWindow =
-        nsPIDOMWindowOuter::From(aParent)->GetTop();
+        nsPIDOMWindowOuter::From(aParent)->GetInProcessTop();
     if (parentTopWindow) {
       parentTopInnerWindow = parentTopWindow->GetCurrentInnerWindow();
     }
diff --git a/dom/jsurl/nsJSProtocolHandler.cpp b/dom/jsurl/nsJSProtocolHandler.cpp
index aaf67e71ea7f..a0a2ec66904e 100644
--- a/dom/jsurl/nsJSProtocolHandler.cpp
+++ b/dom/jsurl/nsJSProtocolHandler.cpp
@@ -594,7 +594,8 @@ nsJSChannel::AsyncOpen(nsIStreamListener* aListener) {
     nsLoadFlags loadFlags;
     mStreamChannel->GetLoadFlags(&loadFlags);
     if (loadFlags & LOAD_DOCUMENT_URI) {
-      mDocumentOnloadBlockedOn = mDocumentOnloadBlockedOn->GetParentDocument();
+      mDocumentOnloadBlockedOn =
+          mDocumentOnloadBlockedOn->GetInProcessParentDocument();
     }
   }
   if (mDocumentOnloadBlockedOn) {
diff --git a/dom/media/AutoplayPolicy.cpp b/dom/media/AutoplayPolicy.cpp
index 97a6dddc36ed..eac424c30d81 100644
--- a/dom/media/AutoplayPolicy.cpp
+++ b/dom/media/AutoplayPolicy.cpp
@@ -40,7 +40,7 @@ static Document* ApproverDocOf(const Document& aDocument) {
   }
 
   nsCOMPtr<nsIDocShellTreeItem> rootTreeItem;
-  ds->GetSameTypeRootTreeItem(getter_AddRefs(rootTreeItem));
+  ds->GetInProcessSameTypeRootTreeItem(getter_AddRefs(rootTreeItem));
   if (!rootTreeItem) {
     return nullptr;
   }
diff --git a/dom/media/BackgroundVideoDecodingPermissionObserver.cpp b/dom/media/BackgroundVideoDecodingPermissionObserver.cpp
index 27bfdc938f95..eebbbc960db6 100644
--- a/dom/media/BackgroundVideoDecodingPermissionObserver.cpp
+++ b/dom/media/BackgroundVideoDecodingPermissionObserver.cpp
@@ -142,7 +142,7 @@ BackgroundVideoDecodingPermissionObserver::GetOwnerWindow() const {
     return nullptr;
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> topWin = outerWin->GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topWin = outerWin->GetInProcessTop();
   return topWin.forget();
 }
 
@@ -166,7 +166,7 @@ bool BackgroundVideoDecodingPermissionObserver::IsValidEventSender(
     return false;
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> senderTop = senderOuter->GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> senderTop = senderOuter->GetInProcessTop();
   if (!senderTop) {
     return false;
   }
diff --git a/dom/media/MediaManager.cpp b/dom/media/MediaManager.cpp
index aa8e9d9dad62..dbdefcb25742 100644
--- a/dom/media/MediaManager.cpp
+++ b/dom/media/MediaManager.cpp
@@ -3929,10 +3929,10 @@ void MediaManager::IterateWindowListeners(nsPIDOMWindowInner* aWindow,
     nsCOMPtr<nsIDocShell> docShell = aWindow->GetDocShell();
     if (docShell) {
       int32_t i, count;
-      docShell->GetChildCount(&count);
+      docShell->GetInProcessChildCount(&count);
       for (i = 0; i < count; ++i) {
         nsCOMPtr<nsIDocShellTreeItem> item;
-        docShell->GetChildAt(i, getter_AddRefs(item));
+        docShell->GetInProcessChildAt(i, getter_AddRefs(item));
         nsCOMPtr<nsPIDOMWindowOuter> winOuter =
             item ? item->GetWindow() : nullptr;
 
diff --git a/dom/media/eme/MediaKeys.cpp b/dom/media/eme/MediaKeys.cpp
index 44d810c7f4f5..b6ca48c4fbf9 100644
--- a/dom/media/eme/MediaKeys.cpp
+++ b/dom/media/eme/MediaKeys.cpp
@@ -421,7 +421,8 @@ already_AddRefed<DetailedPromise> MediaKeys::Init(ErrorResult& aRv) {
         NS_LITERAL_CSTRING("Couldn't get top-level window in MediaKeys::Init"));
     return promise.forget();
   }
-  nsCOMPtr<nsPIDOMWindowOuter> top = window->GetOuterWindow()->GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> top =
+      window->GetOuterWindow()->GetInProcessTop();
   if (!top || !top->GetExtantDoc()) {
     promise->MaybeReject(
         NS_ERROR_DOM_INVALID_STATE_ERR,
diff --git a/dom/payments/PaymentRequest.cpp b/dom/payments/PaymentRequest.cpp
index fa94be79dbee..c6c1eea59502 100644
--- a/dom/payments/PaymentRequest.cpp
+++ b/dom/payments/PaymentRequest.cpp
@@ -1128,12 +1128,12 @@ bool PaymentRequest::InFullyActiveDocument() {
 
   // According to the definition of the fully active document, recursive
   // checking the parent document are all IsCurrentActiveDocument
-  Document* parentDoc = doc->GetParentDocument();
+  Document* parentDoc = doc->GetInProcessParentDocument();
   while (parentDoc) {
     if (parentDoc && !parentDoc->IsCurrentActiveDocument()) {
       return false;
     }
-    parentDoc = parentDoc->GetParentDocument();
+    parentDoc = parentDoc->GetInProcessParentDocument();
   }
   return true;
 }
diff --git a/dom/payments/PaymentRequestManager.cpp b/dom/payments/PaymentRequestManager.cpp
index 2f53bb399b16..89e0632c2396 100644
--- a/dom/payments/PaymentRequestManager.cpp
+++ b/dom/payments/PaymentRequestManager.cpp
@@ -500,7 +500,8 @@ nsresult PaymentRequestManager::CreatePayment(
 
   nsCOMPtr<nsPIDOMWindowOuter> outerWindow = aWindow->GetOuterWindow();
   MOZ_ASSERT(outerWindow);
-  if (nsCOMPtr<nsPIDOMWindowOuter> topOuterWindow = outerWindow->GetTop()) {
+  if (nsCOMPtr<nsPIDOMWindowOuter> topOuterWindow =
+          outerWindow->GetInProcessTop()) {
     outerWindow = topOuterWindow;
   }
   uint64_t topOuterWindowId = outerWindow->WindowID();
diff --git a/dom/performance/PerformanceTiming.cpp b/dom/performance/PerformanceTiming.cpp
index 0c21e0886265..ae4bef6c9bc1 100644
--- a/dom/performance/PerformanceTiming.cpp
+++ b/dom/performance/PerformanceTiming.cpp
@@ -623,7 +623,8 @@ bool PerformanceTiming::IsTopLevelContentDocument() const {
     return false;
   }
   nsCOMPtr<nsIDocShellTreeItem> rootItem;
-  Unused << docShell->GetSameTypeRootTreeItem(getter_AddRefs(rootItem));
+  Unused << docShell->GetInProcessSameTypeRootTreeItem(
+      getter_AddRefs(rootItem));
   if (rootItem.get() != static_cast<nsIDocShellTreeItem*>(docShell.get())) {
     return false;
   }
diff --git a/dom/plugins/base/nsPluginInstanceOwner.cpp b/dom/plugins/base/nsPluginInstanceOwner.cpp
index f887c069ec44..b46e9ab4f038 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -2813,7 +2813,8 @@ NS_IMETHODIMP nsPluginInstanceOwner::CreateWidget(void) {
       // created in chrome.
       if (XRE_IsContentProcess()) {
         if (nsCOMPtr<nsPIDOMWindowOuter> window = doc->GetWindow()) {
-          if (nsCOMPtr<nsPIDOMWindowOuter> topWindow = window->GetTop()) {
+          if (nsCOMPtr<nsPIDOMWindowOuter> topWindow =
+                  window->GetInProcessTop()) {
             dom::BrowserChild* tc = dom::BrowserChild::GetFrom(topWindow);
             if (tc) {
               // This returns a PluginWidgetProxy which remotes a number of
diff --git a/dom/presentation/PresentationRequest.cpp b/dom/presentation/PresentationRequest.cpp
index 4004b395b229..fd2f1fc08851 100644
--- a/dom/presentation/PresentationRequest.cpp
+++ b/dom/presentation/PresentationRequest.cpp
@@ -469,7 +469,7 @@ bool PresentationRequest::IsProhibitMixedSecurityContexts(Document* aDocument) {
       return true;
     }
 
-    doc = doc->GetParentDocument();
+    doc = doc->GetInProcessParentDocument();
   }
 
   return false;
diff --git a/dom/script/ScriptLoader.cpp b/dom/script/ScriptLoader.cpp
index f4e7a0d418e2..c8e9753bff1f 100644
--- a/dom/script/ScriptLoader.cpp
+++ b/dom/script/ScriptLoader.cpp
@@ -3139,7 +3139,8 @@ bool ScriptLoader::ReadyToExecuteParserBlockingScripts() {
     return false;
   }
 
-  for (Document* doc = mDocument; doc; doc = doc->GetParentDocument()) {
+  for (Document* doc = mDocument; doc;
+       doc = doc->GetInProcessParentDocument()) {
     ScriptLoader* ancestor = doc->ScriptLoader();
     if (!ancestor->SelfReadyToExecuteParserBlockingScripts() &&
         ancestor->AddPendingChildLoader(this)) {
diff --git a/dom/security/FramingChecker.cpp b/dom/security/FramingChecker.cpp
index d9d9bc6e0b98..cd58980e249e 100644
--- a/dom/security/FramingChecker.cpp
+++ b/dom/security/FramingChecker.cpp
@@ -118,7 +118,7 @@ bool FramingChecker::CheckOneFrameOptionsPolicy(nsIHttpChannel* aHttpChannel,
   if (!aPolicy.LowerCaseEqualsLiteral("deny") &&
       !aPolicy.LowerCaseEqualsLiteral("sameorigin")) {
     nsCOMPtr<nsIDocShellTreeItem> root;
-    curDocShellItem->GetSameTypeRootTreeItem(getter_AddRefs(root));
+    curDocShellItem->GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
     ReportError("XFOInvalid", root, uri, aPolicy);
     return true;
   }
@@ -138,9 +138,10 @@ bool FramingChecker::CheckOneFrameOptionsPolicy(nsIHttpChannel* aHttpChannel,
     return true;
   }
 
-  // GetScriptableTop, not GetTop, because we want this to respect
+  // GetInProcessScriptableTop, not GetTop, because we want this to respect
   // <iframe mozbrowser> boundaries.
-  nsCOMPtr<nsPIDOMWindowOuter> topWindow = thisWindow->GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topWindow =
+      thisWindow->GetInProcessScriptableTop();
 
   // if the document is in the top window, it's not in a frame.
   if (thisWindow == topWindow) {
@@ -155,8 +156,8 @@ bool FramingChecker::CheckOneFrameOptionsPolicy(nsIHttpChannel* aHttpChannel,
   // Traverse up the parent chain and stop when we see a docshell whose
   // parent has a system principal, or a docshell corresponding to
   // <iframe mozbrowser>.
-  while (NS_SUCCEEDED(
-             curDocShellItem->GetParent(getter_AddRefs(parentDocShellItem))) &&
+  while (NS_SUCCEEDED(curDocShellItem->GetInProcessParent(
+             getter_AddRefs(parentDocShellItem))) &&
          parentDocShellItem) {
     nsCOMPtr<nsIDocShell> curDocShell = do_QueryInterface(curDocShellItem);
     if (curDocShell && curDocShell->GetIsMozBrowser()) {
diff --git a/dom/security/nsCSPContext.cpp b/dom/security/nsCSPContext.cpp
index d7318da29c0a..6863dea52632 100644
--- a/dom/security/nsCSPContext.cpp
+++ b/dom/security/nsCSPContext.cpp
@@ -1473,7 +1473,8 @@ nsCSPContext::PermitsAncestry(nsIDocShell* aDocShell,
   nsCOMPtr<nsIURI> uriClone;
 
   // iterate through each docShell parent item
-  while (NS_SUCCEEDED(treeItem->GetParent(getter_AddRefs(parentTreeItem))) &&
+  while (NS_SUCCEEDED(
+             treeItem->GetInProcessParent(getter_AddRefs(parentTreeItem))) &&
          parentTreeItem != nullptr) {
     // stop when reaching chrome
     if (parentTreeItem->ItemType() == nsIDocShellTreeItem::typeChrome) {
diff --git a/dom/security/nsMixedContentBlocker.cpp b/dom/security/nsMixedContentBlocker.cpp
index 81b06808ed3b..a42402e104ca 100644
--- a/dom/security/nsMixedContentBlocker.cpp
+++ b/dom/security/nsMixedContentBlocker.cpp
@@ -90,7 +90,7 @@ class nsMixedContentEvent : public Runnable {
       return NS_OK;
     }
     nsCOMPtr<nsIDocShellTreeItem> sameTypeRoot;
-    docShell->GetSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
+    docShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
     NS_ASSERTION(
         sameTypeRoot,
         "No document shell root tree item from document shell tree item!");
@@ -852,7 +852,7 @@ nsresult nsMixedContentBlocker::ShouldLoad(
 
   // Get the sameTypeRoot tree item from the docshell
   nsCOMPtr<nsIDocShellTreeItem> sameTypeRoot;
-  docShell->GetSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
+  docShell->GetInProcessSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
   NS_ASSERTION(sameTypeRoot, "No root tree item from docshell!");
 
   // When navigating an iframe, the iframe may be https
@@ -899,7 +899,8 @@ nsresult nsMixedContentBlocker::ShouldLoad(
 
       // update the parent to the grandparent.
       nsCOMPtr<nsIDocShellTreeItem> newParentTreeItem;
-      parentTreeItem->GetSameTypeParent(getter_AddRefs(newParentTreeItem));
+      parentTreeItem->GetInProcessSameTypeParent(
+          getter_AddRefs(newParentTreeItem));
       parentTreeItem = newParentTreeItem;
     }  // end while loop.
 
diff --git a/dom/system/nsDeviceSensors.cpp b/dom/system/nsDeviceSensors.cpp
index 5699b8970fbb..c650e32fc621 100644
--- a/dom/system/nsDeviceSensors.cpp
+++ b/dom/system/nsDeviceSensors.cpp
@@ -212,7 +212,7 @@ static bool WindowCannotReceiveSensorEvent(nsPIDOMWindowInner* aWindow) {
   }
 
   // Check to see if this window is a cross-origin iframe
-  nsCOMPtr<nsPIDOMWindowOuter> top = aWindow->GetScriptableTop();
+  nsCOMPtr<nsPIDOMWindowOuter> top = aWindow->GetInProcessScriptableTop();
   nsCOMPtr<nsIScriptObjectPrincipal> sop = do_QueryInterface(aWindow);
   nsCOMPtr<nsIScriptObjectPrincipal> topSop = do_QueryInterface(top);
   if (!sop || !topSop) {
diff --git a/dom/websocket/WebSocket.cpp b/dom/websocket/WebSocket.cpp
index dfcf18e65d68..a21b40fdf49c 100644
--- a/dom/websocket/WebSocket.cpp
+++ b/dom/websocket/WebSocket.cpp
@@ -1178,7 +1178,8 @@ class AsyncOpenRunnable final : public WebSocketMainThreadRunnable {
     }
 
     uint64_t windowID = 0;
-    nsCOMPtr<nsPIDOMWindowOuter> topWindow = aWindow->GetScriptableTop();
+    nsCOMPtr<nsPIDOMWindowOuter> topWindow =
+        aWindow->GetInProcessScriptableTop();
     nsCOMPtr<nsPIDOMWindowInner> topInner;
     if (topWindow) {
       topInner = topWindow->GetCurrentInnerWindow();
@@ -1400,7 +1401,8 @@ already_AddRefed<WebSocket> WebSocket::ConstructorCommon(
     }
 
     uint64_t windowID = 0;
-    nsCOMPtr<nsPIDOMWindowOuter> topWindow = outerWindow->GetScriptableTop();
+    nsCOMPtr<nsPIDOMWindowOuter> topWindow =
+        outerWindow->GetInProcessScriptableTop();
     nsCOMPtr<nsPIDOMWindowInner> topInner;
     if (topWindow) {
       topInner = topWindow->GetCurrentInnerWindow();
@@ -2719,7 +2721,7 @@ nsresult WebSocketImpl::GetLoadingPrincipal(nsIPrincipal** aPrincipal) {
     }
 
     nsCOMPtr<nsPIDOMWindowOuter> parentWindow =
-        innerWindow->GetScriptableParent();
+        innerWindow->GetInProcessScriptableParent();
     if (NS_WARN_IF(!parentWindow)) {
       return NS_ERROR_DOM_SECURITY_ERR;
     }
@@ -2744,7 +2746,8 @@ nsresult WebSocketImpl::GetLoadingPrincipal(nsIPrincipal** aPrincipal) {
         break;
       }
 
-      if (parentWindow->GetScriptableTop() == innerWindow->GetScriptableTop()) {
+      if (parentWindow->GetInProcessScriptableTop() ==
+          innerWindow->GetInProcessScriptableTop()) {
         break;
       }
 
diff --git a/dom/workers/WorkerDebugger.cpp b/dom/workers/WorkerDebugger.cpp
index 3110a5a6e174..4b908a004e9a 100644
--- a/dom/workers/WorkerDebugger.cpp
+++ b/dom/workers/WorkerDebugger.cpp
@@ -482,7 +482,7 @@ RefPtr<PerformanceInfoPromise> WorkerDebugger::ReportPerformanceInfo() {
   if (win) {
     nsPIDOMWindowOuter* outer = win->GetOuterWindow();
     if (outer) {
-      top = outer->GetTop();
+      top = outer->GetInProcessTop();
       if (top) {
         windowID = top->WindowID();
         isTopLevel = outer->IsTopLevelWindow();
diff --git a/dom/workers/WorkerPrivate.cpp b/dom/workers/WorkerPrivate.cpp
index 45f3d42c7bbf..8db98a591592 100644
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -2508,7 +2508,7 @@ nsresult WorkerPrivate::GetLoadInfo(JSContext* aCx, nsPIDOMWindowInner* aWindow,
         if (document->GetSandboxFlags() & SANDBOXED_ORIGIN) {
           nsCOMPtr<Document> tmpDoc = document;
           do {
-            tmpDoc = tmpDoc->GetParentDocument();
+            tmpDoc = tmpDoc->GetInProcessParentDocument();
           } while (tmpDoc && tmpDoc->GetSandboxFlags() & SANDBOXED_ORIGIN);
 
           if (tmpDoc) {
diff --git a/dom/xhr/XMLHttpRequestMainThread.cpp b/dom/xhr/XMLHttpRequestMainThread.cpp
index 79c84f2dd062..e0c7fd3036e7 100644
--- a/dom/xhr/XMLHttpRequestMainThread.cpp
+++ b/dom/xhr/XMLHttpRequestMainThread.cpp
@@ -2890,7 +2890,7 @@ nsresult XMLHttpRequestMainThread::SendInternal(const BodyExtractorBase* aBody,
 
     if (GetOwner()) {
       if (nsCOMPtr<nsPIDOMWindowOuter> topWindow =
-              GetOwner()->GetOuterWindow()->GetTop()) {
+              GetOwner()->GetOuterWindow()->GetInProcessTop()) {
         if (nsCOMPtr<nsPIDOMWindowInner> topInner =
                 topWindow->GetCurrentInnerWindow()) {
           mSuspendedDoc = topWindow->GetExtantDoc();
diff --git a/dom/xul/XULPersist.cpp b/dom/xul/XULPersist.cpp
index d73aba5c9004..36511e9bbf72 100644
--- a/dom/xul/XULPersist.cpp
+++ b/dom/xul/XULPersist.cpp
@@ -19,7 +19,7 @@ static bool ShouldPersistAttribute(Element* aElement, nsAtom* aAttribute) {
   if (aElement->IsXULElement(nsGkAtoms::window)) {
     // This is not an element of the top document, its owner is
     // not an nsXULWindow. Persist it.
-    if (aElement->OwnerDoc()->GetParentDocument()) {
+    if (aElement->OwnerDoc()->GetInProcessParentDocument()) {
       return true;
     }
     // The following attributes of xul:window should be handled in
diff --git a/editor/spellchecker/EditorSpellCheck.cpp b/editor/spellchecker/EditorSpellCheck.cpp
index e14096a9867c..16662691d24a 100644
--- a/editor/spellchecker/EditorSpellCheck.cpp
+++ b/editor/spellchecker/EditorSpellCheck.cpp
@@ -635,7 +635,7 @@ EditorSpellCheck::UpdateCurrentDictionary(
   mEditor->GetFlags(&flags);
   if (flags & nsIPlaintextEditor::eEditorMailMask) {
     RefPtr<Document> ownerDoc = rootContent->OwnerDoc();
-    Document* parentDoc = ownerDoc->GetParentDocument();
+    Document* parentDoc = ownerDoc->GetInProcessParentDocument();
     if (parentDoc) {
       rootContent = parentDoc->GetDocumentElement();
       if (!rootContent) {
diff --git a/image/ImageCacheKey.cpp b/image/ImageCacheKey.cpp
index 008072627c55..487e7e50e7d6 100644
--- a/image/ImageCacheKey.cpp
+++ b/image/ImageCacheKey.cpp
@@ -193,7 +193,8 @@ nsCString ImageCacheKey::GetTopLevelBaseDomain(Document* aDocument,
   // unique image cache per the top-level document eTLD+1.
   if (!AntiTrackingCommon::MaybeIsFirstPartyStorageAccessGrantedFor(
           aDocument->GetInnerWindow(), aURI)) {
-    nsPIDOMWindowOuter* top = aDocument->GetInnerWindow()->GetScriptableTop();
+    nsPIDOMWindowOuter* top =
+        aDocument->GetInnerWindow()->GetInProcessScriptableTop();
     nsPIDOMWindowInner* topInner = top ? top->GetCurrentInnerWindow() : nullptr;
     if (!topInner) {
       return aDocument
diff --git a/layout/base/AccessibleCaretEventHub.cpp b/layout/base/AccessibleCaretEventHub.cpp
index dee44871f228..c297eeb0dc26 100644
--- a/layout/base/AccessibleCaretEventHub.cpp
+++ b/layout/base/AccessibleCaretEventHub.cpp
@@ -357,7 +357,7 @@ void AccessibleCaretEventHub::Init() {
     curDocShell->AddWeakScrollObserver(this);
 
     nsCOMPtr<nsIDocShellTreeItem> tmp;
-    curDocShell->GetSameTypeParent(getter_AddRefs(tmp));
+    curDocShell->GetInProcessSameTypeParent(getter_AddRefs(tmp));
     curDocShell = do_QueryInterface(tmp);
   } while (curDocShell);
 
@@ -383,7 +383,7 @@ void AccessibleCaretEventHub::Terminate() {
     curDocShell->RemoveWeakScrollObserver(this);
 
     nsCOMPtr<nsIDocShellTreeItem> tmp;
-    curDocShell->GetSameTypeParent(getter_AddRefs(tmp));
+    curDocShell->GetInProcessSameTypeParent(getter_AddRefs(tmp));
     curDocShell = do_QueryInterface(tmp);
   }
 
diff --git a/layout/base/PresShell.cpp b/layout/base/PresShell.cpp
index c197526c7a2b..3d0e13f18156 100644
--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -6357,7 +6357,7 @@ already_AddRefed<PresShell> PresShell::GetParentPresShellForEventHandling() {
   NS_ENSURE_TRUE(treeItem, nullptr);
 
   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
-  treeItem->GetParent(getter_AddRefs(parentTreeItem));
+  treeItem->GetInProcessParent(getter_AddRefs(parentTreeItem));
   nsCOMPtr<nsIDocShell> parentDocShell = do_QueryInterface(parentTreeItem);
   NS_ENSURE_TRUE(parentDocShell && treeItem != parentTreeItem, nullptr);
 
@@ -7157,7 +7157,7 @@ nsIFrame* PresShell::EventHandler::GetFrameForHandlingEventWith(
     }
     Document* retargetEventDoc = aRetargetDocument;
     while (!retargetPresShell) {
-      retargetEventDoc = retargetEventDoc->GetParentDocument();
+      retargetEventDoc = retargetEventDoc->GetInProcessParentDocument();
       if (!retargetEventDoc) {
         return nullptr;
       }
@@ -8244,7 +8244,7 @@ PresShell::EventHandler::GetDocumentURIToCompareWithBlacklist(
   // get URI of the parent document.
   for (Document* document = presContext->Document();
        document && document->IsContentDocument();
-       document = document->GetParentDocument()) {
+       document = document->GetInProcessParentDocument()) {
     // The document URI may be about:blank even if it comes from actual web
     // site.  Therefore, we need to check the URI of its principal.
     nsIPrincipal* principal = document->NodePrincipal();
diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index 05cf175f49ae..130288e889a6 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -4159,7 +4159,7 @@ nsCSSFrameConstructor::FindXULMenubarData(const Element& aElement,
   nsCOMPtr<nsIDocShell> treeItem = aElement.OwnerDoc()->GetDocShell();
   if (treeItem && nsIDocShellTreeItem::typeChrome == treeItem->ItemType()) {
     nsCOMPtr<nsIDocShellTreeItem> parent;
-    treeItem->GetParent(getter_AddRefs(parent));
+    treeItem->GetInProcessParent(getter_AddRefs(parent));
     if (!parent) {
       // This is the root.  Suppress the menubar, since on Mac
       // window menus are not attached to the window.
diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index 31cbfc58292a..be0c828bedee 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -672,7 +672,7 @@ nsresult nsDocumentViewer::SyncParentSubDocMap() {
   }
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  docShell->GetParent(getter_AddRefs(parent));
+  docShell->GetInProcessParent(getter_AddRefs(parent));
 
   nsCOMPtr<nsPIDOMWindowOuter> parent_win =
       parent ? parent->GetWindow() : nullptr;
@@ -1104,14 +1104,14 @@ nsDocumentViewer::LoadComplete(nsresult aStatus) {
         nsCOMPtr<nsIDocShell> container(mContainer);
         if (container) {
           int32_t count;
-          container->GetChildCount(&count);
+          container->GetInProcessChildCount(&count);
           // We first find all background loading iframes that need to
           // fire artificial load events, and instead of firing them as
           // soon as we find them, we store them in an array, to prevent
           // us from skipping some events.
           for (int32_t i = 0; i < count; ++i) {
             nsCOMPtr<nsIDocShellTreeItem> child;
-            container->GetChildAt(i, getter_AddRefs(child));
+            container->GetInProcessChildAt(i, getter_AddRefs(child));
             nsCOMPtr<nsIDocShell> childIDocShell = do_QueryInterface(child);
             RefPtr<nsDocShell> docShell = nsDocShell::Cast(childIDocShell);
             if (docShell && docShell->TreatAsBackgroundLoad() &&
@@ -1421,11 +1421,11 @@ nsresult nsDocumentViewer::PermitUnloadInternal(uint32_t* aPermitUnloadFlags,
 
   if (docShell) {
     int32_t childCount;
-    docShell->GetChildCount(&childCount);
+    docShell->GetInProcessChildCount(&childCount);
 
     for (int32_t i = 0; i < childCount && *aPermitUnload; ++i) {
       nsCOMPtr<nsIDocShellTreeItem> item;
-      docShell->GetChildAt(i, getter_AddRefs(item));
+      docShell->GetInProcessChildAt(i, getter_AddRefs(item));
 
       nsCOMPtr<nsIDocShell> docShell(do_QueryInterface(item));
 
@@ -1538,10 +1538,10 @@ static void AttachContainerRecurse(nsIDocShell* aShell) {
 
   // Now recurse through the children
   int32_t childCount;
-  aShell->GetChildCount(&childCount);
+  aShell->GetInProcessChildCount(&childCount);
   for (int32_t i = 0; i < childCount; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> childItem;
-    aShell->GetChildAt(i, getter_AddRefs(childItem));
+    aShell->GetInProcessChildAt(i, getter_AddRefs(childItem));
     nsCOMPtr<nsIDocShell> shell = do_QueryInterface(childItem);
     AttachContainerRecurse(shell);
   }
@@ -1694,10 +1694,10 @@ static void DetachContainerRecurse(nsIDocShell* aShell) {
 
   // Now recurse through the children
   int32_t childCount;
-  aShell->GetChildCount(&childCount);
+  aShell->GetInProcessChildCount(&childCount);
   for (int32_t i = 0; i < childCount; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> childItem;
-    aShell->GetChildAt(i, getter_AddRefs(childItem));
+    aShell->GetInProcessChildAt(i, getter_AddRefs(childItem));
     nsCOMPtr<nsIDocShell> shell = do_QueryInterface(childItem);
     DetachContainerRecurse(shell);
   }
@@ -1971,10 +1971,10 @@ nsDocumentViewer::SetDocumentInternal(Document* aDocument,
       nsCOMPtr<nsIDocShell> node(mContainer);
       if (node) {
         int32_t count;
-        node->GetChildCount(&count);
+        node->GetInProcessChildCount(&count);
         for (int32_t i = 0; i < count; ++i) {
           nsCOMPtr<nsIDocShellTreeItem> child;
-          node->GetChildAt(0, getter_AddRefs(child));
+          node->GetInProcessChildAt(0, getter_AddRefs(child));
           node->RemoveChild(child);
         }
       }
@@ -2167,7 +2167,7 @@ nsDocumentViewer::Show(void) {
       // We need to find the root DocShell since only that object has an
       // SHistory and we need the SHistory to evict content viewers
       nsCOMPtr<nsIDocShellTreeItem> root;
-      treeItem->GetSameTypeRootTreeItem(getter_AddRefs(root));
+      treeItem->GetInProcessSameTypeRootTreeItem(getter_AddRefs(root));
       nsCOMPtr<nsIWebNavigation> webNav = do_QueryInterface(root);
       RefPtr<ChildSHistory> history = webNav->GetSessionHistory();
       if (history) {
@@ -2669,10 +2669,10 @@ void nsDocumentViewer::CallChildren(CallChildFunc aFunc, void* aClosure) {
   if (docShell) {
     int32_t i;
     int32_t n;
-    docShell->GetChildCount(&n);
+    docShell->GetInProcessChildCount(&n);
     for (i = 0; i < n; i++) {
       nsCOMPtr<nsIDocShellTreeItem> child;
-      docShell->GetChildAt(i, getter_AddRefs(child));
+      docShell->GetInProcessChildAt(i, getter_AddRefs(child));
       nsCOMPtr<nsIDocShell> childAsShell(do_QueryInterface(child));
       NS_ASSERTION(childAsShell, "null child in docshell");
       if (childAsShell) {
@@ -3216,7 +3216,7 @@ nsDocumentViewer::GetContentSize(int32_t* aWidth, int32_t* aHeight) {
   NS_ENSURE_TRUE(docShellAsItem, NS_ERROR_NOT_AVAILABLE);
 
   nsCOMPtr<nsIDocShellTreeItem> docShellParent;
-  docShellAsItem->GetSameTypeParent(getter_AddRefs(docShellParent));
+  docShellAsItem->GetInProcessSameTypeParent(getter_AddRefs(docShellParent));
 
   // It's only valid to access this from a top frame.  Doesn't work from
   // sub-frames.
@@ -3904,7 +3904,7 @@ void nsDocumentViewer::SetIsPrintingInDocShellTree(
     if (aIsPrintingOrPP) {
       while (parentItem) {
         nsCOMPtr<nsIDocShellTreeItem> parent;
-        parentItem->GetSameTypeParent(getter_AddRefs(parent));
+        parentItem->GetInProcessSameTypeParent(getter_AddRefs(parent));
         if (!parent) {
           break;
         }
@@ -3928,10 +3928,10 @@ void nsDocumentViewer::SetIsPrintingInDocShellTree(
 
   // Traverse children to see if any of them are printing.
   int32_t n;
-  aParentNode->GetChildCount(&n);
+  aParentNode->GetInProcessChildCount(&n);
   for (int32_t i = 0; i < n; i++) {
     nsCOMPtr<nsIDocShellTreeItem> child;
-    aParentNode->GetChildAt(i, getter_AddRefs(child));
+    aParentNode->GetInProcessChildAt(i, getter_AddRefs(child));
     NS_ASSERTION(child, "child isn't nsIDocShell");
     if (child) {
       SetIsPrintingInDocShellTree(child, aIsPrintingOrPP, false);
diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index 9b5364d0f257..9543c22196c0 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -7442,7 +7442,7 @@ nsDeviceContext* nsLayoutUtils::GetDeviceContextForScreenInfo(
     }
 
     nsCOMPtr<nsIDocShellTreeItem> parentItem;
-    docShell->GetParent(getter_AddRefs(parentItem));
+    docShell->GetInProcessParent(getter_AddRefs(parentItem));
     docShell = do_QueryInterface(parentItem);
   }
 
diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
index fe9cdd7144e7..1bbae86d1225 100644
--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -612,7 +612,7 @@ nsresult nsPresContext::Init(nsDeviceContext* aDeviceContext) {
     mRefreshDriver =
         mDocument->GetDisplayDocument()->GetPresContext()->RefreshDriver();
   } else {
-    dom::Document* parent = mDocument->GetParentDocument();
+    dom::Document* parent = mDocument->GetInProcessParentDocument();
     // Unfortunately, sometimes |parent| here has no presshell because
     // printing screws up things.  Assert that in other cases it does,
     // but whenever the shell is null just fall back on using our own
@@ -625,7 +625,7 @@ nsresult nsPresContext::Init(nsDeviceContext* aDeviceContext) {
       nsCOMPtr<nsIDocShellTreeItem> ourItem = mDocument->GetDocShell();
       if (ourItem) {
         nsCOMPtr<nsIDocShellTreeItem> parentItem;
-        ourItem->GetSameTypeParent(getter_AddRefs(parentItem));
+        ourItem->GetInProcessSameTypeParent(getter_AddRefs(parentItem));
         if (parentItem) {
           Element* containingElement =
               parent->FindContentForSubDocument(mDocument);
diff --git a/layout/generic/nsPluginFrame.cpp b/layout/generic/nsPluginFrame.cpp
index 10b68fe2cbeb..40263cc7743f 100644
--- a/layout/generic/nsPluginFrame.cpp
+++ b/layout/generic/nsPluginFrame.cpp
@@ -741,7 +741,7 @@ mozilla::LayoutDeviceIntPoint nsPluginFrame::GetRemoteTabChromeOffset() {
   LayoutDeviceIntPoint offset;
   if (XRE_IsContentProcess()) {
     if (nsPIDOMWindowOuter* window = GetContent()->OwnerDoc()->GetWindow()) {
-      if (nsCOMPtr<nsPIDOMWindowOuter> topWindow = window->GetTop()) {
+      if (nsCOMPtr<nsPIDOMWindowOuter> topWindow = window->GetInProcessTop()) {
         dom::BrowserChild* tc = dom::BrowserChild::GetFrom(topWindow);
         if (tc) {
           offset += tc->GetChromeOffset();
diff --git a/layout/printing/PrintPreviewUserEventSuppressor.cpp b/layout/printing/PrintPreviewUserEventSuppressor.cpp
index 60bae773c2b7..a84feeb50b81 100644
--- a/layout/printing/PrintPreviewUserEventSuppressor.cpp
+++ b/layout/printing/PrintPreviewUserEventSuppressor.cpp
@@ -142,7 +142,7 @@ PrintPreviewUserEventSuppressor::HandleEvent(Event* aEvent) {
           Document* doc = content->GetUncomposedDoc();
           NS_ASSERTION(doc, "no document");
 
-          Document* parentDoc = doc->GetParentDocument();
+          Document* parentDoc = doc->GetInProcessParentDocument();
           NS_ASSERTION(parentDoc, "no parent document");
 
           nsCOMPtr<nsPIDOMWindowOuter> win = parentDoc->GetWindow();
diff --git a/layout/style/nsComputedDOMStyle.cpp b/layout/style/nsComputedDOMStyle.cpp
index f7bbcffc80c7..9246aa60e3b6 100644
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -779,7 +779,7 @@ bool nsComputedDOMStyle::NeedsToFlush() const {
   // If parent document is there, also needs to check if there is some change
   // that needs to flush this document (e.g. size change for iframe).
   while (doc->StyleOrLayoutObservablyDependsOnParentDocumentLayout()) {
-    Document* parentDocument = doc->GetParentDocument();
+    Document* parentDocument = doc->GetInProcessParentDocument();
     Element* element = parentDocument->FindContentForSubDocument(doc);
     if (ElementNeedsRestyle(element, nullptr)) {
       return true;
diff --git a/layout/style/nsMediaFeatures.cpp b/layout/style/nsMediaFeatures.cpp
index 96d272b25fc5..166d66d27897 100644
--- a/layout/style/nsMediaFeatures.cpp
+++ b/layout/style/nsMediaFeatures.cpp
@@ -166,7 +166,7 @@ float Gecko_MediaFeatures_GetResolution(const Document* aDocument) {
 
 static const Document* TopDocument(const Document* aDocument) {
   const Document* current = aDocument;
-  while (const Document* parent = current->GetParentDocument()) {
+  while (const Document* parent = current->GetInProcessParentDocument()) {
     current = parent;
   }
   return current;
diff --git a/layout/tools/layout-debug/src/nsLayoutDebuggingTools.cpp b/layout/tools/layout-debug/src/nsLayoutDebuggingTools.cpp
index ac5f405e25c6..c92ca3cee967 100644
--- a/layout/tools/layout-debug/src/nsLayoutDebuggingTools.cpp
+++ b/layout/tools/layout-debug/src/nsLayoutDebuggingTools.cpp
@@ -134,15 +134,15 @@ static void DumpAWebShell(nsIDocShellTreeItem* aShellItem, FILE* out,
 
   fprintf(out, "%p '", static_cast<void*>(aShellItem));
   aShellItem->GetName(name);
-  aShellItem->GetSameTypeParent(getter_AddRefs(parent));
+  aShellItem->GetInProcessSameTypeParent(getter_AddRefs(parent));
   fputs(NS_LossyConvertUTF16toASCII(name).get(), out);
   fprintf(out, "' parent=%p <\n", static_cast<void*>(parent));
 
   ++aIndent;
-  aShellItem->GetChildCount(&n);
+  aShellItem->GetInProcessChildCount(&n);
   for (i = 0; i < n; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> child;
-    aShellItem->GetChildAt(i, getter_AddRefs(child));
+    aShellItem->GetInProcessChildAt(i, getter_AddRefs(child));
     if (child) {
       DumpAWebShell(child, out, aIndent);
     }
@@ -174,10 +174,10 @@ static void DumpContentRecur(nsIDocShell* aDocShell, FILE* out) {
     }
     // dump the frames of the sub documents
     int32_t i, n;
-    aDocShell->GetChildCount(&n);
+    aDocShell->GetInProcessChildCount(&n);
     for (i = 0; i < n; ++i) {
       nsCOMPtr<nsIDocShellTreeItem> child;
-      aDocShell->GetChildAt(i, getter_AddRefs(child));
+      aDocShell->GetInProcessChildAt(i, getter_AddRefs(child));
       nsCOMPtr<nsIDocShell> childAsShell(do_QueryInterface(child));
       if (child) {
         DumpContentRecur(childAsShell, out);
@@ -208,10 +208,10 @@ static void DumpFramesRecur(nsIDocShell* aDocShell, FILE* out) {
 
   // dump the frames of the sub documents
   int32_t i, n;
-  aDocShell->GetChildCount(&n);
+  aDocShell->GetInProcessChildCount(&n);
   for (i = 0; i < n; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> child;
-    aDocShell->GetChildAt(i, getter_AddRefs(child));
+    aDocShell->GetInProcessChildAt(i, getter_AddRefs(child));
     nsCOMPtr<nsIDocShell> childAsShell(do_QueryInterface(child));
     if (childAsShell) {
       DumpFramesRecur(childAsShell, out);
@@ -242,10 +242,10 @@ static void DumpViewsRecur(nsIDocShell* aDocShell, FILE* out) {
 
   // dump the views of the sub documents
   int32_t i, n;
-  aDocShell->GetChildCount(&n);
+  aDocShell->GetInProcessChildCount(&n);
   for (i = 0; i < n; i++) {
     nsCOMPtr<nsIDocShellTreeItem> child;
-    aDocShell->GetChildAt(i, getter_AddRefs(child));
+    aDocShell->GetInProcessChildAt(i, getter_AddRefs(child));
     nsCOMPtr<nsIDocShell> childAsShell(do_QueryInterface(child));
     if (childAsShell) {
       DumpViewsRecur(childAsShell, out);
diff --git a/layout/xul/nsXULPopupManager.cpp b/layout/xul/nsXULPopupManager.cpp
index 515a587d5599..ecdfbb84d879 100644
--- a/layout/xul/nsXULPopupManager.cpp
+++ b/layout/xul/nsXULPopupManager.cpp
@@ -1180,7 +1180,7 @@ bool nsXULPopupManager::IsChildOfDocShell(Document* aDoc,
     if (docShellItem == aExpected) return true;
 
     nsCOMPtr<nsIDocShellTreeItem> parent;
-    docShellItem->GetParent(getter_AddRefs(parent));
+    docShellItem->GetInProcessParent(getter_AddRefs(parent));
     docShellItem = parent;
   }
 
diff --git a/netwerk/base/LoadInfo.cpp b/netwerk/base/LoadInfo.cpp
index f74401038a80..73876f7b5684 100644
--- a/netwerk/base/LoadInfo.cpp
+++ b/netwerk/base/LoadInfo.cpp
@@ -45,7 +45,7 @@ namespace net {
 static uint64_t FindTopOuterWindowID(nsPIDOMWindowOuter* aOuter) {
   nsCOMPtr<nsPIDOMWindowOuter> outer = aOuter;
   while (nsCOMPtr<nsPIDOMWindowOuter> parent =
-             outer->GetScriptableParentOrNull()) {
+             outer->GetInProcessScriptableParentOrNull()) {
     outer = parent;
   }
   return outer->WindowID();
@@ -165,7 +165,8 @@ LoadInfo::LoadInfo(
     if (contextOuter) {
       ComputeIsThirdPartyContext(contextOuter);
       mOuterWindowID = contextOuter->WindowID();
-      nsCOMPtr<nsPIDOMWindowOuter> parent = contextOuter->GetScriptableParent();
+      nsCOMPtr<nsPIDOMWindowOuter> parent =
+          contextOuter->GetInProcessScriptableParent();
       mParentOuterWindowID = parent ? parent->WindowID() : mOuterWindowID;
       mTopOuterWindowID = FindTopOuterWindowID(contextOuter);
       RefPtr<dom::BrowsingContext> bc = contextOuter->GetBrowsingContext();
@@ -205,7 +206,7 @@ LoadInfo::LoadInfo(
           // top-level document's flag, not the iframe document's.
           mDocumentHasLoaded = false;
           nsGlobalWindowOuter* topOuter =
-              innerWindow->GetScriptableTopInternal();
+              innerWindow->GetInProcessScriptableTopInternal();
           if (topOuter) {
             nsGlobalWindowInner* topInner =
                 nsGlobalWindowInner::Cast(topOuter->GetCurrentInnerWindow());
@@ -377,7 +378,8 @@ LoadInfo::LoadInfo(nsPIDOMWindowOuter* aOuterWindow,
 
   // TODO We can have a parent without a frame element in some cases dealing
   // with the hidden window.
-  nsCOMPtr<nsPIDOMWindowOuter> parent = aOuterWindow->GetScriptableParent();
+  nsCOMPtr<nsPIDOMWindowOuter> parent =
+      aOuterWindow->GetInProcessScriptableParent();
   mParentOuterWindowID = parent ? parent->WindowID() : 0;
   mTopOuterWindowID = FindTopOuterWindowID(aOuterWindow);
 
diff --git a/parser/html/nsHtml5TreeOpExecutor.cpp b/parser/html/nsHtml5TreeOpExecutor.cpp
index a297c564bee8..ac43720900d6 100644
--- a/parser/html/nsHtml5TreeOpExecutor.cpp
+++ b/parser/html/nsHtml5TreeOpExecutor.cpp
@@ -800,7 +800,7 @@ void nsHtml5TreeOpExecutor::MaybeComplainAboutCharset(const char* aMsgId,
   // if alerted about them.
   if (!strcmp(aMsgId, "EncNoDeclaration") && mDocShell) {
     nsCOMPtr<nsIDocShellTreeItem> parent;
-    mDocShell->GetSameTypeParent(getter_AddRefs(parent));
+    mDocShell->GetInProcessSameTypeParent(getter_AddRefs(parent));
     if (parent) {
       return;
     }
diff --git a/security/manager/ssl/nsSecureBrowserUIImpl.cpp b/security/manager/ssl/nsSecureBrowserUIImpl.cpp
index d471b04228f7..b9d8d4282da7 100644
--- a/security/manager/ssl/nsSecureBrowserUIImpl.cpp
+++ b/security/manager/ssl/nsSecureBrowserUIImpl.cpp
@@ -113,7 +113,7 @@ nsSecureBrowserUIImpl::PrepareForContentChecks() {
   if (docShell->ItemType() == nsIDocShellTreeItem::typeContent) {
     nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem(docShell);
     nsCOMPtr<nsIDocShellTreeItem> sameTypeRoot;
-    Unused << docShellTreeItem->GetSameTypeRootTreeItem(
+    Unused << docShellTreeItem->GetInProcessSameTypeRootTreeItem(
         getter_AddRefs(sameTypeRoot));
     MOZ_ASSERT(
         sameTypeRoot,
diff --git a/toolkit/components/antitracking/AntiTrackingCommon.cpp b/toolkit/components/antitracking/AntiTrackingCommon.cpp
index 2f14df508e28..6cdb94137afa 100644
--- a/toolkit/components/antitracking/AntiTrackingCommon.cpp
+++ b/toolkit/components/antitracking/AntiTrackingCommon.cpp
@@ -347,7 +347,7 @@ bool CheckContentBlockingAllowList(nsPIDOMWindowInner* aWindow) {
     return entry.Data().mResult;
   }
 
-  nsPIDOMWindowOuter* top = aWindow->GetScriptableTop();
+  nsPIDOMWindowOuter* top = aWindow->GetInProcessScriptableTop();
   if (top) {
     nsIURI* topWinURI = top->GetDocumentURI();
     Document* doc = top->GetExtantDoc();
@@ -605,7 +605,7 @@ already_AddRefed<nsPIDOMWindowOuter> GetTopWindow(nsPIDOMWindowInner* aWindow) {
   nsCOMPtr<nsPIDOMWindowOuter> pwin;
   auto* outer = nsGlobalWindowOuter::Cast(aWindow->GetOuterWindow());
   if (outer) {
-    pwin = outer->GetScriptableTop();
+    pwin = outer->GetInProcessScriptableTop();
   }
 
   if (!pwin) {
@@ -872,7 +872,8 @@ AntiTrackingCommon::AddFirstPartyStorageAccessGrantedFor(
     }
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> topOuterWindow = outerParentWindow->GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topOuterWindow =
+      outerParentWindow->GetInProcessTop();
   nsGlobalWindowOuter* topWindow = nsGlobalWindowOuter::Cast(topOuterWindow);
   if (NS_WARN_IF(!topWindow)) {
     LOG(("No top outer window."));
@@ -1163,7 +1164,7 @@ bool AntiTrackingCommon::IsFirstPartyStorageAccessGrantedFor(
     return false;
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> topOuterWindow = outerWindow->GetTop();
+  nsCOMPtr<nsPIDOMWindowOuter> topOuterWindow = outerWindow->GetInProcessTop();
   nsGlobalWindowOuter* topWindow = nsGlobalWindowOuter::Cast(topOuterWindow);
   if (NS_WARN_IF(!topWindow)) {
     LOG(("No top outer window"));
diff --git a/toolkit/components/browser/nsWebBrowser.cpp b/toolkit/components/browser/nsWebBrowser.cpp
index 2d9b645e7060..bfc5e02cfb7c 100644
--- a/toolkit/components/browser/nsWebBrowser.cpp
+++ b/toolkit/components/browser/nsWebBrowser.cpp
@@ -345,13 +345,13 @@ nsWebBrowser::GetItemType(int32_t* aItemType) {
 }
 
 NS_IMETHODIMP
-nsWebBrowser::GetParent(nsIDocShellTreeItem** aParent) {
+nsWebBrowser::GetInProcessParent(nsIDocShellTreeItem** aParent) {
   *aParent = nullptr;
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsWebBrowser::GetSameTypeParent(nsIDocShellTreeItem** aParent) {
+nsWebBrowser::GetInProcessSameTypeParent(nsIDocShellTreeItem** aParent) {
   *aParent = nullptr;
 
   return NS_OK;
@@ -363,28 +363,31 @@ nsWebBrowser::GetRootTreeItem(nsIDocShellTreeItem** aRootTreeItem) {
   *aRootTreeItem = static_cast<nsIDocShellTreeItem*>(this);
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  NS_ENSURE_SUCCESS(GetParent(getter_AddRefs(parent)), NS_ERROR_FAILURE);
+  NS_ENSURE_SUCCESS(GetInProcessParent(getter_AddRefs(parent)),
+                    NS_ERROR_FAILURE);
   while (parent) {
     *aRootTreeItem = parent;
-    NS_ENSURE_SUCCESS((*aRootTreeItem)->GetParent(getter_AddRefs(parent)),
-                      NS_ERROR_FAILURE);
+    NS_ENSURE_SUCCESS(
+        (*aRootTreeItem)->GetInProcessParent(getter_AddRefs(parent)),
+        NS_ERROR_FAILURE);
   }
   NS_ADDREF(*aRootTreeItem);
   return NS_OK;
 }
 
 NS_IMETHODIMP
-nsWebBrowser::GetSameTypeRootTreeItem(nsIDocShellTreeItem** aRootTreeItem) {
+nsWebBrowser::GetInProcessSameTypeRootTreeItem(
+    nsIDocShellTreeItem** aRootTreeItem) {
   NS_ENSURE_ARG_POINTER(aRootTreeItem);
   *aRootTreeItem = static_cast<nsIDocShellTreeItem*>(this);
 
   nsCOMPtr<nsIDocShellTreeItem> parent;
-  NS_ENSURE_SUCCESS(GetSameTypeParent(getter_AddRefs(parent)),
+  NS_ENSURE_SUCCESS(GetInProcessSameTypeParent(getter_AddRefs(parent)),
                     NS_ERROR_FAILURE);
   while (parent) {
     *aRootTreeItem = parent;
     NS_ENSURE_SUCCESS(
-        (*aRootTreeItem)->GetSameTypeParent(getter_AddRefs(parent)),
+        (*aRootTreeItem)->GetInProcessSameTypeParent(getter_AddRefs(parent)),
         NS_ERROR_FAILURE);
   }
   NS_ADDREF(*aRootTreeItem);
@@ -445,7 +448,7 @@ nsWebBrowser::SetTreeOwner(nsIDocShellTreeOwner* aTreeOwner) {
 //*****************************************************************************
 
 NS_IMETHODIMP
-nsWebBrowser::GetChildCount(int32_t* aChildCount) {
+nsWebBrowser::GetInProcessChildCount(int32_t* aChildCount) {
   NS_ENSURE_ARG_POINTER(aChildCount);
   *aChildCount = 0;
   return NS_OK;
@@ -462,7 +465,8 @@ nsWebBrowser::RemoveChild(nsIDocShellTreeItem* aChild) {
 }
 
 NS_IMETHODIMP
-nsWebBrowser::GetChildAt(int32_t aIndex, nsIDocShellTreeItem** aChild) {
+nsWebBrowser::GetInProcessChildAt(int32_t aIndex,
+                                  nsIDocShellTreeItem** aChild) {
   return NS_ERROR_UNEXPECTED;
 }
 
diff --git a/toolkit/components/extensions/ExtensionPolicyService.cpp b/toolkit/components/extensions/ExtensionPolicyService.cpp
index 7111059dae2f..7b7c96842a95 100644
--- a/toolkit/components/extensions/ExtensionPolicyService.cpp
+++ b/toolkit/components/extensions/ExtensionPolicyService.cpp
@@ -426,7 +426,7 @@ static bool CheckParentFrames(nsPIDOMWindowOuter* aWindow,
   }
 
   auto* piWin = aWindow;
-  while ((piWin = piWin->GetScriptableParentOrNull())) {
+  while ((piWin = piWin->GetInProcessScriptableParentOrNull())) {
     auto* win = nsGlobalWindowOuter::Cast(piWin);
 
     auto* principal = BasePrincipal::Cast(win->GetPrincipal());
diff --git a/toolkit/components/extensions/WebExtensionPolicy.cpp b/toolkit/components/extensions/WebExtensionPolicy.cpp
index 5edb6e9df82e..884a231cd9be 100644
--- a/toolkit/components/extensions/WebExtensionPolicy.cpp
+++ b/toolkit/components/extensions/WebExtensionPolicy.cpp
@@ -774,7 +774,7 @@ bool WindowShouldMatchActiveTab(nsPIDOMWindowOuter* aWin) {
     return false;
   }
 
-  nsCOMPtr<nsPIDOMWindowOuter> parent = aWin->GetParent();
+  nsCOMPtr<nsPIDOMWindowOuter> parent = aWin->GetInProcessParent();
   MOZ_ASSERT(parent != nullptr);
   return WindowShouldMatchActiveTab(parent);
 }
diff --git a/toolkit/components/satchel/nsFormFillController.cpp b/toolkit/components/satchel/nsFormFillController.cpp
index f3784e443396..32b07982015d 100644
--- a/toolkit/components/satchel/nsFormFillController.cpp
+++ b/toolkit/components/satchel/nsFormFillController.cpp
@@ -1438,7 +1438,7 @@ int32_t nsFormFillController::GetIndexOfDocShell(nsIDocShell* aDocShell) {
   // Recursively check the parent docShell of this one
   nsCOMPtr<nsIDocShellTreeItem> treeItem = aDocShell;
   nsCOMPtr<nsIDocShellTreeItem> parentItem;
-  treeItem->GetParent(getter_AddRefs(parentItem));
+  treeItem->GetInProcessParent(getter_AddRefs(parentItem));
   if (parentItem) {
     nsCOMPtr<nsIDocShell> parentShell = do_QueryInterface(parentItem);
     return GetIndexOfDocShell(parentShell);
diff --git a/toolkit/components/sessionstore/SessionStoreUtils.cpp b/toolkit/components/sessionstore/SessionStoreUtils.cpp
index 55eda8244bf3..f15d472688f8 100644
--- a/toolkit/components/sessionstore/SessionStoreUtils.cpp
+++ b/toolkit/components/sessionstore/SessionStoreUtils.cpp
@@ -103,14 +103,14 @@ void SessionStoreUtils::ForEachNonDynamicChildFrame(
   }
 
   int32_t length;
-  aRv = docShell->GetChildCount(&length);
+  aRv = docShell->GetInProcessChildCount(&length);
   if (aRv.Failed()) {
     return;
   }
 
   for (int32_t i = 0; i < length; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> item;
-    docShell->GetChildAt(i, getter_AddRefs(item));
+    docShell->GetInProcessChildAt(i, getter_AddRefs(item));
     if (!item) {
       aRv.Throw(NS_ERROR_FAILURE);
       return;
@@ -1047,13 +1047,13 @@ static void CollectedSessionStorageInternal(
     return;
   }
   int32_t length;
-  nsresult rv = docShell->GetChildCount(&length);
+  nsresult rv = docShell->GetInProcessChildCount(&length);
   if (NS_FAILED(rv)) {
     return;
   }
   for (int32_t i = 0; i < length; ++i) {
     nsCOMPtr<nsIDocShellTreeItem> item;
-    docShell->GetChildAt(i, getter_AddRefs(item));
+    docShell->GetInProcessChildAt(i, getter_AddRefs(item));
     if (!item) {
       return;
     }
diff --git a/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp b/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp
index 566c1e550cf5..65e4e5879526 100644
--- a/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp
+++ b/toolkit/components/typeaheadfind/nsTypeAheadFind.cpp
@@ -372,7 +372,7 @@ nsresult nsTypeAheadFind::FindItNow(bool aIsLinksOnly,
   nsCOMPtr<nsIDocShellTreeItem> rootContentTreeItem;
   nsCOMPtr<nsIDocShell> currentDocShell;
 
-  startingDocShell->GetSameTypeRootTreeItem(
+  startingDocShell->GetInProcessSameTypeRootTreeItem(
       getter_AddRefs(rootContentTreeItem));
   nsCOMPtr<nsIDocShell> rootContentDocShell =
       do_QueryInterface(rootContentTreeItem);
@@ -533,7 +533,7 @@ nsresult nsTypeAheadFind::FindItNow(bool aIsLinksOnly,
             nsCOMPtr<nsIDocShellTreeItem> fwTreeItem(fwPI->GetDocShell());
             if (NS_SUCCEEDED(rv)) {
               nsCOMPtr<nsIDocShellTreeItem> fwRootTreeItem;
-              rv = fwTreeItem->GetSameTypeRootTreeItem(
+              rv = fwTreeItem->GetInProcessSameTypeRootTreeItem(
                   getter_AddRefs(fwRootTreeItem));
               if (NS_SUCCEEDED(rv) && fwRootTreeItem == rootContentTreeItem)
                 shouldFocusEditableElement = true;
diff --git a/toolkit/components/windowwatcher/nsWindowWatcher.cpp b/toolkit/components/windowwatcher/nsWindowWatcher.cpp
index 7855be6fc831..6e6b88db6a80 100644
--- a/toolkit/components/windowwatcher/nsWindowWatcher.cpp
+++ b/toolkit/components/windowwatcher/nsWindowWatcher.cpp
@@ -852,7 +852,8 @@ nsresult nsWindowWatcher::OpenWindowInternal(
 
       nsCOMPtr<nsPIDOMWindowInner> parentTopInnerWindow;
       if (parentWindow) {
-        nsCOMPtr<nsPIDOMWindowOuter> parentTopWindow = parentWindow->GetTop();
+        nsCOMPtr<nsPIDOMWindowOuter> parentTopWindow =
+            parentWindow->GetInProcessTop();
         if (parentTopWindow) {
           parentTopInnerWindow = parentTopWindow->GetCurrentInnerWindow();
         }
diff --git a/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp b/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp
index 1f73fd8cdcc9..9c721ac315ca 100644
--- a/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp
+++ b/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp
@@ -112,7 +112,7 @@ bool AddonManagerWebAPI::IsAPIEnabled(JSContext* aCx, JSObject* aGlobal) {
     // Checks whether there is a parent frame of the same type. This won't cross
     // mozbrowser or chrome boundaries.
     nsCOMPtr<nsIDocShellTreeItem> parent;
-    nsresult rv = docShell->GetSameTypeParent(getter_AddRefs(parent));
+    nsresult rv = docShell->GetInProcessSameTypeParent(getter_AddRefs(parent));
     if (NS_FAILED(rv)) {
       return false;
     }
@@ -128,7 +128,7 @@ bool AddonManagerWebAPI::IsAPIEnabled(JSContext* aCx, JSObject* aGlobal) {
       return false;
     }
 
-    doc = doc->GetParentDocument();
+    doc = doc->GetInProcessParentDocument();
     if (!doc) {
       // Getting here means something has been torn down so fail safe.
       return false;
diff --git a/uriloader/base/nsDocLoader.cpp b/uriloader/base/nsDocLoader.cpp
index 235b7e181911..a9665a085ded 100644
--- a/uriloader/base/nsDocLoader.cpp
+++ b/uriloader/base/nsDocLoader.cpp
@@ -981,7 +981,7 @@ nsDocLoader::GetIsTopLevel(bool* aResult) {
     nsCOMPtr<nsPIDOMWindowOuter> piwindow = nsPIDOMWindowOuter::From(window);
     NS_ENSURE_STATE(piwindow);
 
-    nsCOMPtr<nsPIDOMWindowOuter> topWindow = piwindow->GetTop();
+    nsCOMPtr<nsPIDOMWindowOuter> topWindow = piwindow->GetInProcessTop();
     *aResult = piwindow == topWindow;
   }
 
diff --git a/widget/SharedWidgetUtils.cpp b/widget/SharedWidgetUtils.cpp
index 22f33aa58427..f1c71b5c6678 100644
--- a/widget/SharedWidgetUtils.cpp
+++ b/widget/SharedWidgetUtils.cpp
@@ -40,7 +40,7 @@ already_AddRefed<nsIWidget> WidgetUtils::DOMWindowToWidget(
         if (!docShellAsItem) return nullptr;
 
         nsCOMPtr<nsIDocShellTreeItem> parent;
-        docShellAsItem->GetParent(getter_AddRefs(parent));
+        docShellAsItem->GetInProcessParent(getter_AddRefs(parent));
 
         window = do_GetInterface(parent);
         if (!window) return nullptr;