bug 939049 - get rid of useless QIs r=smaug

accessible/src/base/Logging.cpp

@@ -99,22 +99,19 @@ LogDocShellState(nsIDocument* aDocumentNode)
   printf("docshell busy: ");
 
   nsAutoCString docShellBusy;
-  nsCOMPtr<nsISupports> container = aDocumentNode->GetContainer();
-  if (container) {
-    nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
-    uint32_t busyFlags = nsIDocShell::BUSY_FLAGS_NONE;
-    docShell->GetBusyFlags(&busyFlags);
-    if (busyFlags == nsIDocShell::BUSY_FLAGS_NONE)
-      printf("'none'");
-    if (busyFlags & nsIDocShell::BUSY_FLAGS_BUSY)
-      printf("'busy'");
-    if (busyFlags & nsIDocShell::BUSY_FLAGS_BEFORE_PAGE_LOAD)
-      printf(", 'before page load'");
-    if (busyFlags & nsIDocShell::BUSY_FLAGS_PAGE_LOADING)
-      printf(", 'page loading'");
-  } else {
+  nsCOMPtr<nsIDocShell> docShell = aDocumentNode->GetDocShell();
+  uint32_t busyFlags = nsIDocShell::BUSY_FLAGS_NONE;
+  docShell->GetBusyFlags(&busyFlags);
+  if (busyFlags == nsIDocShell::BUSY_FLAGS_NONE)
+    printf("'none'");
+  if (busyFlags & nsIDocShell::BUSY_FLAGS_BUSY)
+    printf("'busy'");
+  if (busyFlags & nsIDocShell::BUSY_FLAGS_BEFORE_PAGE_LOAD)
+    printf(", 'before page load'");
+  if (busyFlags & nsIDocShell::BUSY_FLAGS_PAGE_LOADING)
+    printf(", 'page loading'");
+
     printf("[failed]");
-  }
 }
 
 static void
@@ -132,8 +129,7 @@ static void
 LogDocShellTree(nsIDocument* aDocumentNode)
 {
   if (aDocumentNode->IsActive()) {
-    nsCOMPtr<nsISupports> container = aDocumentNode->GetContainer();
-    nsCOMPtr<nsIDocShellTreeItem> treeItem(do_QueryInterface(container));
+    nsCOMPtr<nsIDocShellTreeItem> treeItem(aDocumentNode->GetDocShell());
     nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
     treeItem->GetParent(getter_AddRefs(parentTreeItem));
     nsCOMPtr<nsIDocShellTreeItem> rootTreeItem;

accessible/src/base/nsAccessibilityService.cpp

@@ -200,8 +200,7 @@ nsAccessibilityService::GetRootDocumentAccessible(nsIPresShell* aPresShell,
   nsIPresShell* ps = aPresShell;
   nsIDocument* documentNode = aPresShell->GetDocument();
   if (documentNode) {
-    nsCOMPtr<nsISupports> container = documentNode->GetContainer();
-    nsCOMPtr<nsIDocShellTreeItem> treeItem(do_QueryInterface(container));
+    nsCOMPtr<nsIDocShellTreeItem> treeItem(documentNode->GetDocShell());
     if (treeItem) {
       nsCOMPtr<nsIDocShellTreeItem> rootTreeItem;
       treeItem->GetRootTreeItem(getter_AddRefs(rootTreeItem));

accessible/src/base/nsCoreUtils.cpp

@@ -394,17 +394,14 @@ nsCoreUtils::GetDocShellFor(nsINode *aNode)
   if (!aNode)
     return nullptr;
 
-  nsCOMPtr<nsISupports> container = aNode->OwnerDoc()->GetContainer();
-  nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
+  nsCOMPtr<nsIDocShell> docShell = aNode->OwnerDoc()->GetDocShell();
   return docShell.forget();
 }
 
 bool
 nsCoreUtils::IsRootDocument(nsIDocument *aDocument)
 {
-  nsCOMPtr<nsISupports> container = aDocument->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem =
-    do_QueryInterface(container);
+  nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem = aDocument->GetDocShell();
   NS_ASSERTION(docShellTreeItem, "No document shell for document!");
 
   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
@@ -416,9 +413,7 @@ nsCoreUtils::IsRootDocument(nsIDocument *aDocument)
 bool
 nsCoreUtils::IsContentDocument(nsIDocument *aDocument)
 {
-  nsCOMPtr<nsISupports> container = aDocument->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem =
-    do_QueryInterface(container);
+  nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem = aDocument->GetDocShell();
   NS_ASSERTION(docShellTreeItem, "No document shell tree item for document!");
 
   int32_t contentType;
@@ -429,8 +424,7 @@ nsCoreUtils::IsContentDocument(nsIDocument *aDocument)
 bool
 nsCoreUtils::IsTabDocument(nsIDocument* aDocumentNode)
 {
-  nsCOMPtr<nsISupports> container = aDocumentNode->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> treeItem(do_QueryInterface(container));
+  nsCOMPtr<nsIDocShellTreeItem> treeItem(aDocumentNode->GetDocShell());
 
   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
   treeItem->GetParent(getter_AddRefs(parentTreeItem));

accessible/src/generic/Accessible.cpp

@@ -377,10 +377,8 @@ Accessible::AccessKey() const
   nsIDocument* document = mContent->GetCurrentDoc();
   if (!document)
     return KeyBinding();
-  nsCOMPtr<nsISupports> container = document->GetContainer();
-  if (!container)
-    return KeyBinding();
-  nsCOMPtr<nsIDocShellTreeItem> treeItem(do_QueryInterface(container));
+
+  nsCOMPtr<nsIDocShellTreeItem> treeItem(document->GetDocShell());
   if (!treeItem)
     return KeyBinding();
 
@@ -1294,9 +1292,7 @@ Accessible::NativeAttributes()
                                            nsCoreUtils::GetRoleContent(doc));
 
     // Allow ARIA live region markup from outer documents to override
-    nsCOMPtr<nsISupports> container = doc->GetContainer(); 
-    nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem =
-      do_QueryInterface(container);
+    nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem = doc->GetDocShell();
     if (!docShellTreeItem)
       break;
 

accessible/src/generic/DocAccessible.cpp

@@ -688,8 +688,7 @@ DocAccessible::GetBoundsRect(nsRect& aBounds, nsIFrame** aRelativeFrame)
 nsresult
 DocAccessible::AddEventListeners()
 {
-  nsCOMPtr<nsISupports> container = mDocumentNode->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem(do_QueryInterface(container));
+  nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem(mDocumentNode->GetDocShell());
 
   // We want to add a command observer only if the document is content and has
   // an editor.
@@ -721,8 +720,7 @@ DocAccessible::RemoveEventListeners()
   if (mDocumentNode) {
     mDocumentNode->RemoveObserver(this);
 
-    nsCOMPtr<nsISupports> container = mDocumentNode->GetContainer();
-    nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem(do_QueryInterface(container));
+    nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem(mDocumentNode->GetDocShell());
     NS_ASSERTION(docShellTreeItem, "doc should support nsIDocShellTreeItem.");
 
     if (docShellTreeItem) {
@@ -1994,8 +1992,7 @@ DocAccessible::ShutdownChildrenInSubtree(Accessible* aAccessible)
 bool
 DocAccessible::IsLoadEventTarget() const
 {
-  nsCOMPtr<nsISupports> container = mDocumentNode->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> treeItem = do_QueryInterface(container);
+  nsCOMPtr<nsIDocShellTreeItem> treeItem = mDocumentNode->GetDocShell();
   NS_ASSERTION(treeItem, "No document shell for document!");
 
   nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;

content/base/public/nsIDocument.h

@@ -1165,6 +1165,11 @@ public:
    */
   nsILoadContext* GetLoadContext() const;
 
+  /**
+   * Get docshell the for this document.
+   */
+  nsIDocShell* GetDocShell() const;
+
   /**
    * Set and get XML declaration. If aVersion is null there is no declaration.
    * aStandalone takes values -1, 0 and 1 indicating respectively that there
@@ -1525,7 +1530,7 @@ public:
   void SetDisplayDocument(nsIDocument* aDisplayDocument)
   {
     NS_PRECONDITION(!GetShell() &&
-                    !nsCOMPtr<nsISupports>(GetContainer()) &&
+                    !GetContainer() &&
                     !GetWindow(),
                     "Shouldn't set mDisplayDocument on documents that already "
                     "have a presentation or a docshell or a window");

content/base/src/nsContentUtils.cpp

@@ -2626,10 +2626,7 @@ nsContentUtils::CanLoadImage(nsIURI* aURI, nsISupports* aContext,
   uint32_t appType = nsIDocShell::APP_TYPE_UNKNOWN;
 
   {
-    nsCOMPtr<nsISupports> container = aLoadingDocument->GetContainer();
-    nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem =
-      do_QueryInterface(container);
-
+    nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem = aLoadingDocument->GetDocShell();
     if (docShellTreeItem) {
       nsCOMPtr<nsIDocShellTreeItem> root;
       docShellTreeItem->GetRootTreeItem(getter_AddRefs(root));
@@ -3157,8 +3154,7 @@ nsContentUtils::IsChromeDoc(nsIDocument *aDocument)
 bool
 nsContentUtils::IsChildOfSameType(nsIDocument* aDoc)
 {
-  nsCOMPtr<nsISupports> container = aDoc->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> docShellAsItem(do_QueryInterface(container));
+  nsCOMPtr<nsIDocShellTreeItem> docShellAsItem(aDoc->GetDocShell());
   nsCOMPtr<nsIDocShellTreeItem> sameTypeParent;
   if (docShellAsItem) {
     docShellAsItem->GetSameTypeParent(getter_AddRefs(sameTypeParent));
@@ -3239,8 +3235,7 @@ nsContentUtils::IsInChromeDocshell(nsIDocument *aDocument)
     return IsInChromeDocshell(aDocument->GetDisplayDocument());
   }
 
-  nsCOMPtr<nsISupports> docContainer = aDocument->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> docShell(do_QueryInterface(docContainer));
+  nsCOMPtr<nsIDocShellTreeItem> docShell(aDocument->GetDocShell());
   int32_t itemType = nsIDocShellTreeItem::typeContent;
   if (docShell) {
     docShell->GetItemType(&itemType);
@@ -4980,8 +4975,7 @@ nsContentUtils::HidePopupsInDocument(nsIDocument* aDocument)
 #ifdef MOZ_XUL
   nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
   if (pm && aDocument) {
-    nsCOMPtr<nsISupports> container = aDocument->GetContainer();
-    nsCOMPtr<nsIDocShellTreeItem> docShellToHide = do_QueryInterface(container);
+    nsCOMPtr<nsIDocShellTreeItem> docShellToHide = aDocument->GetDocShell();
     if (docShellToHide)
       pm->HidePopupsInDocShell(docShellToHide);
   }
@@ -5881,8 +5875,7 @@ nsContentUtils::IsSubDocumentTabbable(nsIContent* aContent)
     return false;
   }
 
-  nsCOMPtr<nsISupports> container = subDoc->GetContainer();
-  nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
+  nsCOMPtr<nsIDocShell> docShell = subDoc->GetDocShell();
   if (!docShell) {
     return false;
   }
@@ -6016,8 +6009,7 @@ nsContentUtils::FindPresShellForDocument(const nsIDocument* aDoc)
     return shell;
   }
 
-  nsCOMPtr<nsISupports> container = doc->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem = do_QueryInterface(container);
+  nsCOMPtr<nsIDocShellTreeItem> docShellTreeItem = doc->GetDocShell();
   while (docShellTreeItem) {
     // We may be in a display:none subdocument, or we may not have a presshell
     // created yet.

content/base/src/nsDocument.cpp

@@ -8869,12 +8869,11 @@ nsIDocument::CreateStaticClone(nsIDocShell* aCloneContainer)
   mCreatingStaticClone = true;
 
   // Make document use different container during cloning.
-  nsCOMPtr<nsISupports> originalContainer = GetContainer();
-  nsCOMPtr<nsIDocShell> originalShell = do_QueryInterface(originalContainer);
+  nsRefPtr<nsDocShell> originalShell = mDocumentContainer.get();
   SetContainer(static_cast<nsDocShell*>(aCloneContainer));
   nsCOMPtr<nsIDOMNode> clonedNode;
   nsresult rv = domDoc->CloneNode(true, 1, getter_AddRefs(clonedNode));
-  SetContainer(static_cast<nsDocShell*>(originalShell.get()));
+  SetContainer(originalShell);
 
   nsCOMPtr<nsIDocument> clonedDoc;
   if (NS_SUCCEEDED(rv)) {
@@ -10180,8 +10179,7 @@ nsDocument::FullScreenStackTop()
 static bool
 IsInActiveTab(nsIDocument* aDoc)
 {
-  nsCOMPtr<nsISupports> container = aDoc->GetContainer();
-  nsCOMPtr<nsIDocShell> docshell = do_QueryInterface(container);
+  nsCOMPtr<nsIDocShell> docshell = aDoc->GetDocShell();
   if (!docshell) {
     return false;
   }
@@ -10192,12 +10190,8 @@ IsInActiveTab(nsIDocument* aDoc)
     return false;
   }
 
-  nsCOMPtr<nsIDocShellTreeItem> dsti = do_QueryInterface(container);
-  if (!dsti) {
-    return false;
-  }
   nsCOMPtr<nsIDocShellTreeItem> rootItem;
-  dsti->GetRootTreeItem(getter_AddRefs(rootItem));
+  docshell->GetRootTreeItem(getter_AddRefs(rootItem));
   if (!rootItem) {
     return false;
   }
@@ -10856,7 +10850,7 @@ nsDocument::ShouldLockPointer(Element* aElement, Element* aCurrentLock,
 
   // Check if the element is in a document with a docshell.
   nsCOMPtr<nsIDocument> ownerDoc = aElement->OwnerDoc();
-  if (!nsCOMPtr<nsISupports>(ownerDoc->GetContainer())) {
+  if (!ownerDoc->GetContainer()) {
     return false;
   }
   nsCOMPtr<nsPIDOMWindow> ownerWindow = ownerDoc->GetWindow();
@@ -11427,12 +11421,13 @@ nsIDocument::SetContentTypeInternal(const nsACString& aType)
 nsILoadContext*
 nsIDocument::GetLoadContext() const
 {
-  nsCOMPtr<nsISupports> container = GetContainer();
-  if (container) {
-    nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(container);
-    return loadContext;
-  }
-  return nullptr;
+  return mDocumentContainer;
+}
+
+nsIDocShell*
+nsIDocument::GetDocShell() const
+{
+  return mDocumentContainer;
 }
 
 void

content/base/src/nsTreeSanitizer.cpp

@@ -1359,8 +1359,7 @@ nsTreeSanitizer::Sanitize(nsIDocument* aDocument)
   // here that notifies / does not notify or that fires mutation events if
   // in tree.
 #ifdef DEBUG
-  nsCOMPtr<nsISupports> container = aDocument->GetContainer();
-  NS_PRECONDITION(!container, "The document is in a shell.");
+  NS_PRECONDITION(!aDocument->GetContainer(), "The document is in a shell.");
   nsRefPtr<mozilla::dom::Element> root = aDocument->GetRootElement();
   NS_PRECONDITION(root->IsHTML(nsGkAtoms::html), "Not HTML root.");
 #endif

content/html/content/src/HTMLInputElement.cpp

@@ -993,9 +993,7 @@ UploadLastDir::FetchDirectoryAndDisplayPicker(nsIDocument* aDoc,
   nsIURI* docURI = aDoc->GetDocumentURI();
   NS_PRECONDITION(docURI, "docURI is null");
 
-  nsCOMPtr<nsISupports> container = aDoc->GetContainer();
-  nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(container);
-
+  nsCOMPtr<nsILoadContext> loadContext = aDoc->GetLoadContext();
   nsCOMPtr<nsIContentPrefCallback2> prefCallback = 
     new UploadLastDir::ContentPrefCallback(aFilePicker, aFpCallback);
 
@@ -1046,8 +1044,7 @@ UploadLastDir::StoreLastUsedDirectory(nsIDocument* aDoc, nsIFile* aDir)
     return NS_ERROR_OUT_OF_MEMORY;
   prefValue->SetAsAString(unicodePath);
 
-  nsCOMPtr<nsISupports> container = aDoc->GetContainer();
-  nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(container);
+  nsCOMPtr<nsILoadContext> loadContext = aDoc->GetLoadContext();
   return contentPrefService->Set(spec, CPS_PREF_NAME, prefValue, loadContext, nullptr);
 }
 

content/html/content/src/HTMLMediaElement.cpp

@@ -1083,12 +1083,9 @@ nsresult HTMLMediaElement::LoadResource()
   }
 
   // Check if media is allowed for the docshell.
-  nsCOMPtr<nsISupports> container = OwnerDoc()->GetContainer();
-  if (container) {
-    nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
-    if (docShell && !docShell->GetAllowMedia()) {
-      return NS_ERROR_FAILURE;
-    }
+  nsCOMPtr<nsIDocShell> docShell = OwnerDoc()->GetDocShell();
+  if (docShell && !docShell->GetAllowMedia()) {
+    return NS_ERROR_FAILURE;
   }
 
   int16_t shouldLoad = nsIContentPolicy::ACCEPT;

content/xul/document/src/XULDocument.cpp

@@ -3180,8 +3180,7 @@ XULDocument::DoneWalking()
         // Before starting layout, check whether we're a toplevel chrome
         // window.  If we are, set our chrome flags now, so that we don't have
         // to restyle the whole frame tree after StartLayout.
-        nsCOMPtr<nsISupports> container = GetContainer();
-        nsCOMPtr<nsIDocShellTreeItem> item = do_QueryInterface(container);
+        nsCOMPtr<nsIDocShellTreeItem> item = GetDocShell();
         if (item) {
             nsCOMPtr<nsIDocShellTreeOwner> owner;
             item->GetTreeOwner(getter_AddRefs(owner));
@@ -3189,7 +3188,7 @@ XULDocument::DoneWalking()
             if (xulWin) {
                 nsCOMPtr<nsIDocShell> xulWinShell;
                 xulWin->GetDocShell(getter_AddRefs(xulWinShell));
-                if (SameCOMIdentity(xulWinShell, container)) {
+                if (SameCOMIdentity(xulWinShell, item)) {
                     // We're the chrome document!  Apply our chrome flags now.
                     xulWin->ApplyChromeFlags();
                 }

dom/ipc/TabChild.cpp

@@ -2476,8 +2476,7 @@ TabChild::GetFrom(nsIPresShell* aPresShell)
   if (!doc) {
       return nullptr;
   }
-  nsCOMPtr<nsISupports> container = doc->GetContainer();
-  nsCOMPtr<nsIDocShell> docShell(do_QueryInterface(container));
+  nsCOMPtr<nsIDocShell> docShell(doc->GetDocShell());
   return GetFrom(docShell);
 }
 

dom/ipc/TabParent.cpp

@@ -842,10 +842,7 @@ TabParent::RecvSetStatus(const uint32_t& aType, const nsString& aStatus)
 {
   nsCOMPtr<nsIContent> frame = do_QueryInterface(mFrameElement);
   if (frame) {
-    nsCOMPtr<nsISupports> container = frame->OwnerDoc()->GetContainer();
-    if (!container)
-      return true;
-    nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
+    nsCOMPtr<nsIDocShell> docShell = frame->OwnerDoc()->GetDocShell();
     if (!docShell)
       return true;
     nsCOMPtr<nsIDocShellTreeOwner> treeOwner;

editor/composer/src/nsEditorSpellCheck.cpp

@@ -97,8 +97,7 @@ GetLoadContext(nsIEditor* aEditor)
   nsCOMPtr<nsIDocument> doc = do_QueryInterface(domDoc);
   NS_ENSURE_TRUE(doc, nullptr);
 
-  nsCOMPtr<nsISupports> container = doc->GetContainer();
-  nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(container);
+  nsCOMPtr<nsILoadContext> loadContext = doc->GetLoadContext();
   return loadContext.forget();
 }
 

editor/libeditor/base/nsEditorUtils.cpp

@@ -189,8 +189,7 @@ nsEditorHookUtils::GetHookEnumeratorFromDocument(nsIDOMDocument *aDoc,
   nsCOMPtr<nsIDocument> doc = do_QueryInterface(aDoc);
   NS_ENSURE_TRUE(doc, NS_ERROR_FAILURE);
 
-  nsCOMPtr<nsISupports> container = doc->GetContainer();
-  nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
+  nsCOMPtr<nsIDocShell> docShell = doc->GetDocShell();
   nsCOMPtr<nsIClipboardDragDropHookList> hookObj = do_GetInterface(docShell);
   NS_ENSURE_TRUE(hookObj, NS_ERROR_FAILURE);
 

editor/libeditor/text/nsPlaintextDataTransfer.cpp

@@ -432,8 +432,7 @@ bool nsPlaintextEditor::IsSafeToInsertData(nsIDOMDocument* aSourceDoc)
 
   nsCOMPtr<nsIDocument> destdoc = GetDocument();
   NS_ASSERTION(destdoc, "Where is our destination doc?");
-  nsCOMPtr<nsISupports> container = destdoc->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> dsti = do_QueryInterface(container);
+  nsCOMPtr<nsIDocShellTreeItem> dsti = destdoc->GetDocShell();
   nsCOMPtr<nsIDocShellTreeItem> root;
   if (dsti)
     dsti->GetRootTreeItem(getter_AddRefs(root));

layout/base/nsPresContext.cpp

@@ -958,9 +958,7 @@ nsPresContext::Init(nsDeviceContext* aDeviceContext)
                    "How did we get a presshell?");
 
       // We don't have our container set yet at this point
-      nsCOMPtr<nsISupports> ourContainer = mDocument->GetContainer();
-
-      nsCOMPtr<nsIDocShellTreeItem> ourItem = do_QueryInterface(ourContainer);
+      nsCOMPtr<nsIDocShellTreeItem> ourItem = mDocument->GetDocShell();
       if (ourItem) {
         nsCOMPtr<nsIDocShellTreeItem> parentItem;
         ourItem->GetSameTypeParent(getter_AddRefs(parentItem));

layout/generic/nsSubDocumentFrame.cpp

@@ -981,8 +981,7 @@ EndSwapDocShellsForDocument(nsIDocument* aDocument, void*)
   // Our docshell and view trees have been updated for the new hierarchy.
   // Now also update all nsDeviceContext::mWidget to that of the
   // container view in the new hierarchy.
-  nsCOMPtr<nsISupports> container = aDocument->GetContainer();
-  nsCOMPtr<nsIDocShell> ds = do_QueryInterface(container);
+  nsCOMPtr<nsIDocShell> ds = aDocument->GetDocShell();
   if (ds) {
     nsCOMPtr<nsIContentViewer> cv;
     ds->GetContentViewer(getter_AddRefs(cv));

layout/printing/nsPrintEngine.cpp

@@ -1335,8 +1335,7 @@ nsPrintEngine::MapContentForPO(nsPrintObject*   aPO,
   nsIDocument* subDoc = doc->GetSubDocumentFor(aContent);
 
   if (subDoc) {
-    nsCOMPtr<nsISupports> container = subDoc->GetContainer();
-    nsCOMPtr<nsIDocShell> docShell(do_QueryInterface(container));
+    nsCOMPtr<nsIDocShell> docShell(subDoc->GetDocShell());
 
     if (docShell) {
       nsPrintObject * po = nullptr;

layout/style/nsFontFaceLoader.cpp

@@ -876,15 +876,13 @@ nsUserFontSet::CheckFontLoad(const gfxFontFaceSrc* aFontFaceSrc,
   }
 
   *aBypassCache = false;
-  nsCOMPtr<nsISupports> container = ps->GetDocument()->GetContainer();
-  if (container) {
-    nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
-    if (docShell) {
-      uint32_t loadType;
-      if (NS_SUCCEEDED(docShell->GetLoadType(&loadType))) {
-        if ((loadType >> 16) & nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE) {
-          *aBypassCache = true;
-        }
+
+  nsCOMPtr<nsIDocShell> docShell = ps->GetDocument()->GetDocShell();
+  if (docShell) {
+    uint32_t loadType;
+    if (NS_SUCCEEDED(docShell->GetLoadType(&loadType))) {
+      if ((loadType >> 16) & nsIWebNavigation::LOAD_FLAGS_BYPASS_CACHE) {
+        *aBypassCache = true;
       }
     }
   }
@@ -982,11 +980,6 @@ nsUserFontSet::GetPrivateBrowsing()
     return false;
   }
 
-  nsCOMPtr<nsISupports> container = ps->GetDocument()->GetContainer();
-  if (!container) {
-    return false;
-  }
-
-  nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(container);
+  nsCOMPtr<nsILoadContext> loadContext = ps->GetDocument()->GetLoadContext();
   return loadContext && loadContext->UsePrivateBrowsing();
 }

layout/xul/base/src/nsContainerBoxObject.cpp

@@ -80,13 +80,8 @@ NS_IMETHODIMP nsContainerBoxObject::GetDocShell(nsIDocShell** aResult)
     return NS_OK;
   }
 
-  nsCOMPtr<nsISupports> container = sub_doc->GetContainer();
-
-  if (!container) {
-    return NS_OK;
-  }
-
-  return CallQueryInterface(container, aResult);
+  NS_IF_ADDREF(*aResult = sub_doc->GetDocShell());
+  return NS_OK;
 }
 
 nsresult

layout/xul/base/src/nsXULPopupManager.cpp

@@ -1061,8 +1061,7 @@ nsXULPopupManager::HidePopupsInList(const nsTArray<nsMenuPopupFrame *> &aFrames,
 bool
 nsXULPopupManager::IsChildOfDocShell(nsIDocument* aDoc, nsIDocShellTreeItem* aExpected)
 {
-  nsCOMPtr<nsISupports> doc = aDoc->GetContainer();
-  nsCOMPtr<nsIDocShellTreeItem> docShellItem(do_QueryInterface(doc));
+  nsCOMPtr<nsIDocShellTreeItem> docShellItem(aDoc->GetDocShell());
   while(docShellItem) {
     if (docShellItem == aExpected)
       return true;

toolkit/components/satchel/nsFormFillController.cpp

@@ -584,9 +584,8 @@ nsFormFillController::GetInPrivateContext(bool *aInPrivateContext)
   nsCOMPtr<nsIDOMElement> element = do_QueryInterface(mFocusedInput);
   element->GetOwnerDocument(getter_AddRefs(inputDoc));
   nsCOMPtr<nsIDocument> doc = do_QueryInterface(inputDoc);
-  nsCOMPtr<nsISupports> container = doc->GetContainer();
-  nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
-  nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(docShell);
+  nsCOMPtr<nsIDocShell> docShell = doc->GetDocShell();
+  nsCOMPtr<nsILoadContext> loadContext = doc->GetLoadContext();
   *aInPrivateContext = loadContext && loadContext->UsePrivateBrowsing();
   return NS_OK;
 }