--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -4899,17 +4899,17 @@ nsCSSFrameConstructor::ConstructScrollab
 
 nsIFrame*
 nsCSSFrameConstructor::ConstructScrollableBlockWithConstructor(
   nsFrameConstructorState& aState,
   FrameConstructionItem& aItem,
   nsContainerFrame* aParentFrame,
   const nsStyleDisplay* aDisplay,
   nsFrameItems& aFrameItems,
-  BlockFrameCreationFunc aConstructor)
+  ContainerFrameCreationFunc aConstructor)
 {
   nsIContent* const content = aItem.mContent;
   nsStyleContext* const styleContext = aItem.mStyleContext;
 
   nsContainerFrame* newFrame = nullptr;
   RefPtr<nsStyleContext> scrolledContentStyle
     = BeginBuildingScrollFrame(aState, content, styleContext,
                                aState.GetGeometricParent(aDisplay, aParentFrame),
@@ -4951,17 +4951,17 @@ nsCSSFrameConstructor::ConstructNonScrol
 
 nsIFrame*
 nsCSSFrameConstructor::ConstructNonScrollableBlockWithConstructor(
   nsFrameConstructorState& aState,
   FrameConstructionItem& aItem,
   nsContainerFrame* aParentFrame,
   const nsStyleDisplay* aDisplay,
   nsFrameItems& aFrameItems,
-  BlockFrameCreationFunc aConstructor)
+  ContainerFrameCreationFunc aConstructor)
 {
   nsStyleContext* const styleContext = aItem.mStyleContext;
 
   // We want a block formatting context root in paginated contexts for
   // every block that would be scrollable in a non-paginated context.
   // We mark our blocks with a bit here if this condition is true, so
   // we can check it later in nsFrame::ApplyPaginatedOverflowClipping.
   bool clipPaginatedOverflow =
@@ -11111,30 +11111,30 @@ nsCSSFrameConstructor::ProcessChildren(n
                                       nsContentUtils::eXUL_PROPERTIES,
                                       message,
                                       params, ArrayLength(params));
     }
 
     RefPtr<nsStyleContext> blockSC = mPresShell->StyleSet()->
       ResolveInheritingAnonymousBoxStyle(nsCSSAnonBoxes::mozXULAnonymousBlock,
                                          frameStyleContext);
-    nsBlockFrame* blockFrame = NS_NewBlockFrame(mPresShell, blockSC);
+    nsContainerFrame* containerFrame = NS_NewBlockFrame(mPresShell, blockSC);
     // We might, in theory, want to set NS_BLOCK_FLOAT_MGR and
     // NS_BLOCK_MARGIN_ROOT, but I think it's a bad idea given that
     // a real block placed here wouldn't get those set on it.
 
-    InitAndRestoreFrame(aState, aContent, aFrame, blockFrame, false);
-
-    NS_ASSERTION(!blockFrame->HasView(), "need to do view reparenting");
-    ReparentFrames(this, blockFrame, aFrameItems);
-
-    blockFrame->SetInitialChildList(kPrincipalList, aFrameItems);
+    InitAndRestoreFrame(aState, aContent, aFrame, containerFrame, false);
+
+    NS_ASSERTION(!containerFrame->HasView(), "need to do view reparenting");
+    ReparentFrames(this, containerFrame, aFrameItems);
+
+    containerFrame->SetInitialChildList(kPrincipalList, aFrameItems);
     NS_ASSERTION(aFrameItems.IsEmpty(), "How did that happen?");
     aFrameItems.Clear();
-    aFrameItems.AddChild(blockFrame);
+    aFrameItems.AddChild(containerFrame);
 
     aFrame->AddStateBits(NS_STATE_BOX_WRAPS_KIDS_IN_BLOCK);
   }
 }
 
 //----------------------------------------------------------------------
 
 // Support for :first-line style
@@ -12232,29 +12232,29 @@ nsCSSFrameConstructor::CreateIBSiblings(
     // is block-level.
     NS_PRECONDITION(aChildItems.NotEmpty(), "Should have child items");
     NS_PRECONDITION(!aChildItems.FirstChild()->IsInlineOutside(),
                     "Must have list starting with block");
 
     // The initial run of blocks belongs to an anonymous block that we create
     // right now. The anonymous block will be the parent of these block
     // children of the inline.
-    nsBlockFrame* blockFrame = NS_NewBlockFrame(mPresShell, blockSC);
-    InitAndRestoreFrame(aState, content, parentFrame, blockFrame, false);
+    nsContainerFrame* containerFrame = NS_NewBlockFrame(mPresShell, blockSC);
+    InitAndRestoreFrame(aState, content, parentFrame, containerFrame, false);
 
     // Find the first non-block child which defines the end of our block kids
     // and the start of our next inline's kids
     nsFrameList::FrameLinkEnumerator firstNonBlock =
       FindFirstNonBlock(aChildItems);
     nsFrameList blockKids = aChildItems.ExtractHead(firstNonBlock);
 
-    MoveChildrenTo(aInitialInline, blockFrame, blockKids);
-
-    SetFrameIsIBSplit(lastNewInline, blockFrame);
-    aSiblings.AddChild(blockFrame);
+    MoveChildrenTo(aInitialInline, containerFrame, blockKids);
+
+    SetFrameIsIBSplit(lastNewInline, containerFrame);
+    aSiblings.AddChild(containerFrame);
 
     // Now grab the initial inlines in aChildItems and put them into an inline
     // frame.
     nsInlineFrame* inlineFrame = NS_NewInlineFrame(mPresShell, styleContext);
     InitAndRestoreFrame(aState, content, parentFrame, inlineFrame, false);
     inlineFrame->AddStateBits(NS_FRAME_MAY_HAVE_GENERATED_CONTENT |
                               NS_FRAME_CAN_HAVE_ABSPOS_CHILDREN);
     if (aIsPositioned) {
@@ -12264,17 +12264,17 @@ nsCSSFrameConstructor::CreateIBSiblings(
     if (aChildItems.NotEmpty()) {
       nsFrameList::FrameLinkEnumerator firstBlock(aChildItems);
       FindFirstBlock(firstBlock);
       nsFrameList inlineKids = aChildItems.ExtractHead(firstBlock);
 
       MoveChildrenTo(aInitialInline, inlineFrame, inlineKids);
     }
 
-    SetFrameIsIBSplit(blockFrame, inlineFrame);
+    SetFrameIsIBSplit(containerFrame, inlineFrame);
     aSiblings.AddChild(inlineFrame);
     lastNewInline = inlineFrame;
   } while (aChildItems.NotEmpty());
 
   SetFrameIsIBSplit(lastNewInline, nullptr);
 }
 
 void

--- a/layout/base/nsCSSFrameConstructor.h
+++ b/layout/base/nsCSSFrameConstructor.h
@@ -1573,17 +1573,17 @@ private:
    * function.
    */
   nsIFrame* ConstructScrollableBlockWithConstructor(
     nsFrameConstructorState& aState,
     FrameConstructionItem& aItem,
     nsContainerFrame* aParentFrame,
     const nsStyleDisplay* aDisplay,
     nsFrameItems& aFrameItems,
-    BlockFrameCreationFunc aConstructor);
+    ContainerFrameCreationFunc aConstructor);
 
   /**
    * Construct a non-scrollable block frame
    */
   nsIFrame* ConstructNonScrollableBlock(nsFrameConstructorState& aState,
                                         FrameConstructionItem&   aItem,
                                         nsContainerFrame*        aParentFrame,
                                         const nsStyleDisplay*    aDisplay,
@@ -1594,17 +1594,17 @@ private:
    * function.
    */
   nsIFrame* ConstructNonScrollableBlockWithConstructor(
     nsFrameConstructorState& aState,
     FrameConstructionItem& aItem,
     nsContainerFrame* aParentFrame,
     const nsStyleDisplay* aDisplay,
     nsFrameItems& aFrameItems,
-    BlockFrameCreationFunc aConstructor);
+    ContainerFrameCreationFunc aConstructor);
 
   /**
    * This adds FrameConstructionItem objects to aItemsToConstruct for the
    * anonymous content returned by an nsIAnonymousContentCreator::
    * CreateAnonymousContent implementation.
    */
   void AddFCItemsForAnonymousContent(
             nsFrameConstructorState& aState,

--- a/layout/generic/DetailsFrame.cpp
+++ b/layout/generic/DetailsFrame.cpp
@@ -17,17 +17,17 @@ using namespace mozilla::dom;
 
 NS_IMPL_FRAMEARENA_HELPERS(DetailsFrame)
 
 NS_QUERYFRAME_HEAD(DetailsFrame)
   NS_QUERYFRAME_ENTRY(DetailsFrame)
   NS_QUERYFRAME_ENTRY(nsIAnonymousContentCreator)
 NS_QUERYFRAME_TAIL_INHERITING(nsBlockFrame)
 
-nsBlockFrame*
+nsContainerFrame*
 NS_NewDetailsFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
 {
   return new (aPresShell) DetailsFrame(aContext);
 }
 
 namespace mozilla {
 
 DetailsFrame::DetailsFrame(nsStyleContext* aContext)

--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -290,27 +290,27 @@ NS_DECLARE_FRAME_PROPERTY_WITH_DTOR_NEVE
 NS_DECLARE_FRAME_PROPERTY_FRAMELIST(OverflowOutOfFlowsProperty)
 NS_DECLARE_FRAME_PROPERTY_FRAMELIST(PushedFloatProperty)
 NS_DECLARE_FRAME_PROPERTY_FRAMELIST(OutsideBulletProperty)
 NS_DECLARE_FRAME_PROPERTY_WITHOUT_DTOR(InsideBulletProperty, nsBulletFrame)
 NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(BlockEndEdgeOfChildrenProperty, nscoord)
 
 //----------------------------------------------------------------------
 
-nsBlockFrame*
+nsContainerFrame*
 NS_NewBlockFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
 {
   return new (aPresShell) nsBlockFrame(aContext);
 }
 
-nsBlockFrame*
+nsContainerFrame*
 NS_NewBlockFormattingContext(nsIPresShell* aPresShell,
                              nsStyleContext* aStyleContext)
 {
-  nsBlockFrame* blockFrame = NS_NewBlockFrame(aPresShell, aStyleContext);
+  nsContainerFrame* blockFrame = NS_NewBlockFrame(aPresShell, aStyleContext);
   blockFrame->AddStateBits(NS_BLOCK_FORMATTING_CONTEXT_STATE_BITS);
   return blockFrame;
 }
 
 NS_IMPL_FRAMEARENA_HELPERS(nsBlockFrame)
 
 nsBlockFrame::~nsBlockFrame()
 {

--- a/layout/generic/nsBlockFrame.h
+++ b/layout/generic/nsBlockFrame.h
@@ -94,18 +94,18 @@ public:
   ConstLineIterator LinesEnd() const { return mLines.end(); }
   ReverseLineIterator LinesRBegin() { return mLines.rbegin(); }
   ReverseLineIterator LinesREnd() { return mLines.rend(); }
   ConstReverseLineIterator LinesRBegin() const { return mLines.rbegin(); }
   ConstReverseLineIterator LinesREnd() const { return mLines.rend(); }
   LineIterator LinesBeginFrom(nsLineBox* aList) { return mLines.begin(aList); }
   ReverseLineIterator LinesRBeginFrom(nsLineBox* aList) { return mLines.rbegin(aList); }
 
-  friend nsBlockFrame* NS_NewBlockFrame(nsIPresShell* aPresShell,
-                                        nsStyleContext* aContext);
+  friend nsContainerFrame* NS_NewBlockFrame(nsIPresShell* aPresShell,
+                                            nsStyleContext* aContext);
 
   // nsQueryFrame
   NS_DECL_QUERYFRAME
 
   // nsIFrame
   void Init(nsIContent* aContent,
             nsContainerFrame* aParent,
             nsIFrame* aPrevInFlow) override;

--- a/layout/generic/nsHTMLParts.h
+++ b/layout/generic/nsHTMLParts.h
@@ -45,17 +45,17 @@ class ViewportFrame;
                             (NS_BLOCK_FRAME_HAS_OUTSIDE_BULLET | \
                              NS_BLOCK_HAS_FIRST_LETTER_CHILD   | \
                              NS_BLOCK_FRAME_HAS_INSIDE_BULLET)
 
 // Factory methods for creating html layout objects
 
 // Create a frame that supports "display: block" layout behavior
 class nsBlockFrame;
-nsBlockFrame*
+nsContainerFrame*
 NS_NewBlockFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
 
 // Special Generated Content Node. It contains text taken from an
 // attribute of its *grandparent* content node. 
 nsresult
 NS_NewAttributeContent(nsNodeInfoManager *aNodeInfoManager,
                        int32_t aNameSpaceID, nsIAtom* aAttrName,
                        nsIContent** aResult);
@@ -63,17 +63,17 @@ NS_NewAttributeContent(nsNodeInfoManager
 // Create a basic area frame but the GetFrameForPoint is overridden to always
 // return the option frame 
 // By default, area frames will extend
 // their height to cover any children that "stick out".
 nsContainerFrame*
 NS_NewSelectsAreaFrame(nsIPresShell* aPresShell, nsStyleContext* aContext, nsFrameState aFlags);
 
 // Create a block formatting context blockframe
-nsBlockFrame*
+nsContainerFrame*
 NS_NewBlockFormattingContext(nsIPresShell* aPresShell, nsStyleContext* aStyleContext);
 
 nsIFrame*
 NS_NewBRFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
 
 nsIFrame*
 NS_NewCommentFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
 
@@ -170,17 +170,17 @@ NS_NewProgressFrame(nsIPresShell* aPresS
 nsIFrame*
 NS_NewMeterFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
 nsIFrame*
 NS_NewRangeFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
 nsIFrame*
 NS_NewNumberControlFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
 nsIFrame*
 NS_NewDateTimeControlFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
-nsBlockFrame*
+nsContainerFrame*
 NS_NewDetailsFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
 
 // Table frame factories
 class nsTableWrapperFrame;
 nsTableWrapperFrame*
 NS_NewTableWrapperFrame(nsIPresShell* aPresShell, nsStyleContext* aContext);
 class nsTableFrame;
 nsTableFrame*