diff --git a/docshell/base/BrowsingContext.cpp b/docshell/base/BrowsingContext.cpp
index 18ff941db547..f5f2c1f566bd 100644
--- a/docshell/base/BrowsingContext.cpp
+++ b/docshell/base/BrowsingContext.cpp
@@ -13,9 +13,12 @@
 #include "mozilla/dom/BrowsingContextBinding.h"
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Element.h"
 #include "mozilla/dom/Location.h"
 #include "mozilla/dom/LocationBinding.h"
 #include "mozilla/dom/WindowBinding.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+#include "mozilla/dom/WindowGlobalParent.h"
 #include "mozilla/dom/WindowProxyHolder.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/ClearOnShutdown.h"
@@ -201,6 +204,27 @@ void BrowsingContext::SetDocShell(nsIDocShell* aDocShell) {
   mIsInProcess = true;
 }
 
+void BrowsingContext::SetEmbedderElement(Element* aEmbedder) {
+  mEmbedderElement = aEmbedder;
+
+  // Notify the parent process of the embedding status. We don't need to do
+  // this when clearing our embedder, as we're being destroyed either way.
+  if (mEmbedderElement) {
+    nsCOMPtr<nsPIDOMWindowInner> embedderGlobal =
+        do_QueryInterface(mEmbedderElement->GetOwnerGlobal());
+    RefPtr<WindowGlobalChild> wgc = embedderGlobal->GetWindowGlobalChild();
+
+    // If we're in-process, synchronously perform the update to ensure we don't
+    // get out of sync.
+    // XXX(nika): This is super gross, and I don't like it one bit.
+    if (RefPtr<WindowGlobalParent> wgp = wgc->GetParentActor()) {
+      Canonical()->SetEmbedderWindowGlobal(wgp);
+    } else {
+      wgc->SendDidEmbedBrowsingContext(this);
+    }
+  }
+}
+
 void BrowsingContext::Attach(bool aFromIPC) {
   MOZ_LOG(GetLog(), LogLevel::Debug,
           ("%s: %s 0x%08" PRIx64 " to 0x%08" PRIx64,
@@ -518,7 +542,8 @@ bool BrowsingContext::GetUserGestureActivation() {
 NS_IMPL_CYCLE_COLLECTION_CLASS(BrowsingContext)
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(BrowsingContext)
-  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocShell, mChildren, mParent, mGroup)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocShell, mChildren, mParent, mGroup,
+                                  mEmbedderElement)
   if (XRE_IsParentProcess()) {
     CanonicalBrowsingContext::Cast(tmp)->Unlink();
   }
@@ -526,7 +551,8 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(BrowsingContext)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(BrowsingContext)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocShell, mChildren, mParent, mGroup)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocShell, mChildren, mParent, mGroup,
+                                    mEmbedderElement)
   if (XRE_IsParentProcess()) {
     CanonicalBrowsingContext::Cast(tmp)->Traverse(cb);
   }
diff --git a/docshell/base/BrowsingContext.h b/docshell/base/BrowsingContext.h
index 0b8e8f5e65c5..cad6da80849c 100644
--- a/docshell/base/BrowsingContext.h
+++ b/docshell/base/BrowsingContext.h
@@ -46,6 +46,7 @@ class BrowsingContent;
 class BrowsingContextGroup;
 class CanonicalBrowsingContext;
 class ContentParent;
+class Element;
 template <typename>
 struct Nullable;
 template <typename T>
@@ -123,6 +124,11 @@ class BrowsingContext : public nsWrapperCache,
   void SetDocShell(nsIDocShell* aDocShell);
   void ClearDocShell() { mDocShell = nullptr; }
 
+  // Get the embedder element for this BrowsingContext if the embedder is
+  // in-process, or null if it's not.
+  Element* GetEmbedderElement() const { return mEmbedderElement; }
+  void SetEmbedderElement(Element* aEmbedder);
+
   // Get the outer window object for this BrowsingContext if it is in-process
   // and still has a docshell, or null otherwise.
   nsPIDOMWindowOuter* GetDOMWindow() const {
@@ -439,6 +445,8 @@ class BrowsingContext : public nsWrapperCache,
   Children mChildren;
   nsCOMPtr<nsIDocShell> mDocShell;
 
+  RefPtr<Element> mEmbedderElement;
+
   // This is not a strong reference, but using a JS::Heap for that should be
   // fine. The JSObject stored in here should be a proxy with a
   // nsOuterWindowProxy handler, which will update the pointer from its
diff --git a/docshell/base/CanonicalBrowsingContext.cpp b/docshell/base/CanonicalBrowsingContext.cpp
index 5af235c4fb72..46619f67792b 100644
--- a/docshell/base/CanonicalBrowsingContext.cpp
+++ b/docshell/base/CanonicalBrowsingContext.cpp
@@ -116,6 +116,20 @@ void CanonicalBrowsingContext::SetCurrentWindowGlobal(
   mCurrentWindowGlobal = aGlobal;
 }
 
+void CanonicalBrowsingContext::SetEmbedderWindowGlobal(
+    WindowGlobalParent* aGlobal) {
+  MOZ_RELEASE_ASSERT(aGlobal, "null embedder");
+  if (RefPtr<BrowsingContext> parent = GetParent()) {
+    MOZ_RELEASE_ASSERT(aGlobal->BrowsingContext() == parent,
+                       "Embedder has incorrect browsing context");
+  } else {
+    MOZ_RELEASE_ASSERT(aGlobal->IsInProcess(),
+                       "Toplevel must have a parent-process embedder");
+  }
+
+  mEmbedderWindowGlobal = aGlobal;
+}
+
 bool CanonicalBrowsingContext::ValidateTransaction(
     const Transaction& aTransaction, ContentParent* aProcess) {
   // Check that the correct process is performing sets for transactions with
@@ -137,12 +151,14 @@ JSObject* CanonicalBrowsingContext::WrapObject(
 void CanonicalBrowsingContext::Traverse(
     nsCycleCollectionTraversalCallback& cb) {
   CanonicalBrowsingContext* tmp = this;
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mWindowGlobals);
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mWindowGlobals, mCurrentWindowGlobal,
+                                    mEmbedderWindowGlobal);
 }
 
 void CanonicalBrowsingContext::Unlink() {
   CanonicalBrowsingContext* tmp = this;
-  NS_IMPL_CYCLE_COLLECTION_UNLINK(mWindowGlobals);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mWindowGlobals, mCurrentWindowGlobal,
+                                  mEmbedderWindowGlobal);
 }
 
 void CanonicalBrowsingContext::NotifyStartDelayedAutoplayMedia() {
diff --git a/docshell/base/CanonicalBrowsingContext.h b/docshell/base/CanonicalBrowsingContext.h
index 74de53dd05fa..cd639dab7009 100644
--- a/docshell/base/CanonicalBrowsingContext.h
+++ b/docshell/base/CanonicalBrowsingContext.h
@@ -52,6 +52,11 @@ class CanonicalBrowsingContext final : public BrowsingContext {
   }
   void SetCurrentWindowGlobal(WindowGlobalParent* aGlobal);
 
+  WindowGlobalParent* GetEmbedderWindowGlobal() const {
+    return mEmbedderWindowGlobal;
+  }
+  void SetEmbedderWindowGlobal(WindowGlobalParent* aGlobal);
+
   JSObject* WrapObject(JSContext* aCx,
                        JS::Handle<JSObject*> aGivenProto) override;
 
@@ -97,6 +102,7 @@ class CanonicalBrowsingContext final : public BrowsingContext {
   // All live window globals within this browsing context.
   nsTHashtable<nsRefPtrHashKey<WindowGlobalParent>> mWindowGlobals;
   RefPtr<WindowGlobalParent> mCurrentWindowGlobal;
+  RefPtr<WindowGlobalParent> mEmbedderWindowGlobal;
 
   // Generation information for each content process which has interacted with
   // this CanonicalBrowsingContext, by ChildID.
diff --git a/dom/base/nsFrameLoader.cpp b/dom/base/nsFrameLoader.cpp
index 5f198e773a92..8c423dca25fa 100644
--- a/dom/base/nsFrameLoader.cpp
+++ b/dom/base/nsFrameLoader.cpp
@@ -1893,6 +1893,10 @@ void nsFrameLoader::SetOwnerContent(Element* aContent) {
   }
   mOwnerContent = aContent;
 
+  if (RefPtr<BrowsingContext> browsingContext = GetBrowsingContext()) {
+    browsingContext->SetEmbedderElement(mOwnerContent);
+  }
+
   AutoJSAPI jsapi;
   jsapi.Init();
 
@@ -2009,6 +2013,8 @@ nsresult nsFrameLoader::MaybeCreateDocShell() {
   RefPtr<nsDocShell> docShell = nsDocShell::Create(mBrowsingContext);
   NS_ENSURE_TRUE(docShell, NS_ERROR_FAILURE);
 
+  mBrowsingContext->SetEmbedderElement(mOwnerContent);
+
   mIsTopLevelContent =
       mBrowsingContext->IsContent() && !mBrowsingContext->GetParent();
   if (!mNetworkCreated && !mIsTopLevelContent) {
@@ -2604,6 +2610,8 @@ bool nsFrameLoader::TryRemoteBrowser() {
 
   // If we're in a content process, create a BrowserBridgeChild actor.
   if (XRE_IsContentProcess()) {
+    mBrowsingContext->SetEmbedderElement(mOwnerContent);
+
     mBrowserBridgeChild = BrowserBridgeChild::Create(
         this, context, NS_LITERAL_STRING(DEFAULT_REMOTE_TYPE),
         mBrowsingContext);
diff --git a/dom/chrome-webidl/BrowsingContext.webidl b/dom/chrome-webidl/BrowsingContext.webidl
index 918c7bb9571d..e093d19df5be 100644
--- a/dom/chrome-webidl/BrowsingContext.webidl
+++ b/dom/chrome-webidl/BrowsingContext.webidl
@@ -22,6 +22,8 @@ interface BrowsingContext {
 
   readonly attribute nsIDocShell? docShell;
 
+  readonly attribute Element? embedderElement;
+
   readonly attribute unsigned long long id;
 
   readonly attribute BrowsingContext? opener;
@@ -41,6 +43,8 @@ interface CanonicalBrowsingContext : BrowsingContext {
   [Throws]
   readonly attribute DOMString? currentRemoteType;
 
+  readonly attribute WindowGlobalParent? embedderWindowGlobal;
+
   void notifyStartDelayedAutoplayMedia();
 };
 
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 47eb5f9eaeff..bd234a7f4183 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -1148,6 +1148,8 @@ TabParent* ContentParent::CreateBrowser(const TabContext& aContext,
     }
   }
 
+  aBrowsingContext->SetEmbedderElement(aFrameElement);
+
   // Ensure that our content process is subscribed to our newly created
   // BrowsingContextGroup.
   aBrowsingContext->Group()->EnsureSubscribed(constructorSender);
diff --git a/dom/ipc/PWindowGlobal.ipdl b/dom/ipc/PWindowGlobal.ipdl
index f6b80cf95b26..db03c962de2a 100644
--- a/dom/ipc/PWindowGlobal.ipdl
+++ b/dom/ipc/PWindowGlobal.ipdl
@@ -36,6 +36,10 @@ parent:
   /// Notify the parent that this PWindowGlobal is now the current global.
   async BecomeCurrentWindowGlobal();
 
+  /// Notify the parent that this PWindowGlobal has embedded the given
+  /// BrowsingContext.
+  async DidEmbedBrowsingContext(BrowsingContext aContext);
+
   async Destroy();
 };
 
diff --git a/dom/ipc/TabParent.cpp b/dom/ipc/TabParent.cpp
index 4c802d4cebb4..507981c7b6fb 100644
--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -334,6 +334,21 @@ void TabParent::SetOwnerElement(Element* aElement) {
   if (mRenderFrame.IsInitialized()) {
     mRenderFrame.OwnerContentChanged();
   }
+
+  // Set our BrowsingContext's embedder if we're not embedded within a
+  // BrowserBridgeParent.
+  if (!GetBrowserBridgeParent() && mBrowsingContext) {
+    mBrowsingContext->SetEmbedderElement(mFrameElement);
+  }
+
+  // Ensure all TabParent actors within BrowserBridges are also updated.
+  const auto& browserBridges = ManagedPBrowserBridgeParent();
+  for (auto iter = browserBridges.ConstIter(); !iter.Done(); iter.Next()) {
+    BrowserBridgeParent* browserBridge =
+        static_cast<BrowserBridgeParent*>(iter.Get()->GetKey());
+
+    browserBridge->GetTabParent()->SetOwnerElement(aElement);
+  }
 }
 
 NS_IMETHODIMP TabParent::GetOwnerElement(Element** aElement) {
diff --git a/dom/ipc/WindowGlobalParent.cpp b/dom/ipc/WindowGlobalParent.cpp
index 3cb5c980f79f..892f155f48b5 100644
--- a/dom/ipc/WindowGlobalParent.cpp
+++ b/dom/ipc/WindowGlobalParent.cpp
@@ -87,6 +87,12 @@ void WindowGlobalParent::Init(const WindowGlobalInit& aInit) {
   // Attach ourself to the browsing context.
   mBrowsingContext->RegisterWindowGlobal(this);
 
+  // If there is no current window global, assume we're about to become it
+  // optimistically.
+  if (!mBrowsingContext->GetCurrentWindowGlobal()) {
+    mBrowsingContext->SetCurrentWindowGlobal(this);
+  }
+
   // Determine what toplevel frame element our WindowGlobalParent is being
   // embedded in.
   RefPtr<Element> frameElement;
@@ -252,6 +258,13 @@ bool WindowGlobalParent::IsCurrentGlobal() {
   return !mIPCClosed && mBrowsingContext->GetCurrentWindowGlobal() == this;
 }
 
+IPCResult WindowGlobalParent::RecvDidEmbedBrowsingContext(
+    dom::BrowsingContext* aContext) {
+  MOZ_ASSERT(aContext);
+  aContext->Canonical()->SetEmbedderWindowGlobal(this);
+  return IPC_OK();
+}
+
 void WindowGlobalParent::ActorDestroy(ActorDestroyReason aWhy) {
   mIPCClosed = true;
   gWindowGlobalParentsById->Remove(mInnerWindowId);
diff --git a/dom/ipc/WindowGlobalParent.h b/dom/ipc/WindowGlobalParent.h
index ce546d0e5a90..2d61746d5fce 100644
--- a/dom/ipc/WindowGlobalParent.h
+++ b/dom/ipc/WindowGlobalParent.h
@@ -111,6 +111,8 @@ class WindowGlobalParent final : public nsISupports,
   mozilla::ipc::IPCResult RecvAsyncMessage(const nsString& aActorName,
                                            const nsString& aMessageName,
                                            const ClonedMessageData& aData);
+  mozilla::ipc::IPCResult RecvDidEmbedBrowsingContext(
+      dom::BrowsingContext* aContext);
 
   void ActorDestroy(ActorDestroyReason aWhy) override;