--- a/dom/base/nsGkAtomList.h
+++ b/dom/base/nsGkAtomList.h
@@ -1936,17 +1936,16 @@ GK_ATOM(rubyBaseContainerFrame, "RubyBas
 GK_ATOM(rubyBaseFrame, "RubyBaseFrame")
 GK_ATOM(rubyFrame, "RubyFrame")
 GK_ATOM(rubyTextContainerFrame, "RubyTextContainerFrame")
 GK_ATOM(rubyTextFrame, "RubyTextFrame")
 GK_ATOM(scrollFrame, "ScrollFrame")
 GK_ATOM(scrollbarFrame, "ScrollbarFrame")
 GK_ATOM(sequenceFrame, "SequenceFrame")
 GK_ATOM(sliderFrame, "sliderFrame")
-GK_ATOM(tableCaptionFrame, "TableCaptionFrame")
 GK_ATOM(tableCellFrame, "TableCellFrame")
 GK_ATOM(tableColFrame, "TableColFrame")
 GK_ATOM(tableColGroupFrame, "TableColGroupFrame")
 GK_ATOM(tableFrame, "TableFrame")
 GK_ATOM(tableOuterFrame, "TableOuterFrame")
 GK_ATOM(tableRowGroupFrame, "TableRowGroupFrame")
 GK_ATOM(tableRowFrame, "TableRowFrame")
 GK_ATOM(textInputFrame,"TextInputFrame")

--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -1923,17 +1923,17 @@ AdjustCaptionParentFrame(nsContainerFram
 static bool
 GetCaptionAdjustedParent(nsContainerFrame*  aParentFrame,
                          const nsIFrame*    aChildFrame,
                          nsContainerFrame** aAdjParentFrame)
 {
   *aAdjParentFrame = aParentFrame;
   bool haveCaption = false;
 
-  if (nsGkAtoms::tableCaptionFrame == aChildFrame->GetType()) {
+  if (aChildFrame->IsTableCaption()) {
     haveCaption = true;
     *aAdjParentFrame = ::AdjustCaptionParentFrame(aParentFrame);
   }
   return haveCaption;
 }
 
 void
 nsCSSFrameConstructor::AdjustParentFrame(nsContainerFrame**           aParentFrame,
@@ -1950,20 +1950,20 @@ nsCSSFrameConstructor::AdjustParentFrame
     *aParentFrame = ::AdjustCaptionParentFrame(*aParentFrame);
   }
 }
 
 // Pull all the captions present in aItems out  into aCaptions
 static void
 PullOutCaptionFrames(nsFrameItems& aItems, nsFrameItems& aCaptions)
 {
-  nsIFrame *child = aItems.FirstChild();
+  nsIFrame* child = aItems.FirstChild();
   while (child) {
-    nsIFrame *nextSibling = child->GetNextSibling();
-    if (nsGkAtoms::tableCaptionFrame == child->GetType()) {
+    nsIFrame* nextSibling = child->GetNextSibling();
+    if (child->IsTableCaption()) {
       aItems.RemoveFrame(child);
       aCaptions.AddChild(child);
     }
     child = nextSibling;
   }
 }
 
 
@@ -8603,24 +8603,28 @@ nsCSSFrameConstructor::CreateContinuingF
 
   if (nsGkAtoms::textFrame == frameType) {
     newFrame = NS_NewContinuingTextFrame(shell, styleContext);
     newFrame->Init(content, aParentFrame, aFrame);
   } else if (nsGkAtoms::inlineFrame == frameType) {
     newFrame = NS_NewInlineFrame(shell, styleContext);
     newFrame->Init(content, aParentFrame, aFrame);
   } else if (nsGkAtoms::blockFrame == frameType) {
+    MOZ_ASSERT(!aFrame->IsTableCaption(),
+               "no support for fragmenting table captions yet");
     newFrame = NS_NewBlockFrame(shell, styleContext);
     newFrame->Init(content, aParentFrame, aFrame);
 #ifdef MOZ_XUL
   } else if (nsGkAtoms::XULLabelFrame == frameType) {
     newFrame = NS_NewXULLabelFrame(shell, styleContext);
     newFrame->Init(content, aParentFrame, aFrame);
 #endif
   } else if (nsGkAtoms::columnSetFrame == frameType) {
+    MOZ_ASSERT(!aFrame->IsTableCaption(),
+               "no support for fragmenting table captions yet");
     newFrame = NS_NewColumnSetFrame(shell, styleContext, nsFrameState(0));
     newFrame->Init(content, aParentFrame, aFrame);
   } else if (nsGkAtoms::pageFrame == frameType) {
     nsContainerFrame* canvasFrame;
     newFrame = ConstructPageFrame(shell, aPresContext, aParentFrame, aFrame,
                                   canvasFrame);
   } else if (nsGkAtoms::tableOuterFrame == frameType) {
     newFrame =
@@ -9073,17 +9077,17 @@ nsCSSFrameConstructor::MaybeRecreateCont
         // pseudo parent was created for the space, and should now be removed.
         (IsWhitespaceFrame(aFrame) &&
          parent->PrincipalChildList().OnlyChild()) ||
         // If we're a table-column-group, then the GetFirstChild check above is
         // not going to catch cases when we're the first child.
         (inFlowFrame->GetType() == nsGkAtoms::tableColGroupFrame &&
          parent->GetFirstChild(nsIFrame::kColGroupList) == inFlowFrame) ||
         // Similar if we're a table-caption.
-        (inFlowFrame->GetType() == nsGkAtoms::tableCaptionFrame &&
+        (inFlowFrame->IsTableCaption() &&
          parent->GetFirstChild(nsIFrame::kCaptionList) == inFlowFrame)) {
       // We're the first or last frame in the pseudo.  Need to reframe.
       // Good enough to recreate frames for |parent|'s content
       *aResult = RecreateFramesForContent(parent->GetContent(), true, aFlags,
                                           aDestroyedFramesFor);
       return true;
     }
   }

--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -1129,17 +1129,17 @@ nsLayoutUtils::GetChildListNameFor(nsIFr
                  ? nsIFrame::kPopupList
                  : nsIFrame::kPrincipalList;
         }
       } else {
         id = nsIFrame::kPrincipalList;
       }
     } else if (nsGkAtoms::tableColGroupFrame == childType) {
       id = nsIFrame::kColGroupList;
-    } else if (nsGkAtoms::tableCaptionFrame == childType) {
+    } else if (aChildFrame->IsTableCaption()) {
       id = nsIFrame::kCaptionList;
     } else {
       id = nsIFrame::kPrincipalList;
     }
   }
 
 #ifdef DEBUG
   // Verify that the frame is actually in that child list or in the

--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -9447,17 +9447,16 @@ void DR_State::InitFrameTypeTable()
   AddFrameTypeInfo(nsGkAtoms::lineFrame,             "line",      "line");
   AddFrameTypeInfo(nsGkAtoms::listControlFrame,      "select",    "select");
   AddFrameTypeInfo(nsGkAtoms::objectFrame,           "obj",       "object");
   AddFrameTypeInfo(nsGkAtoms::pageFrame,             "page",      "page");
   AddFrameTypeInfo(nsGkAtoms::placeholderFrame,      "place",     "placeholder");
   AddFrameTypeInfo(nsGkAtoms::canvasFrame,           "canvas",    "canvas");
   AddFrameTypeInfo(nsGkAtoms::rootFrame,             "root",      "root");
   AddFrameTypeInfo(nsGkAtoms::scrollFrame,           "scroll",    "scroll");
-  AddFrameTypeInfo(nsGkAtoms::tableCaptionFrame,     "caption",   "tableCaption");
   AddFrameTypeInfo(nsGkAtoms::tableCellFrame,        "cell",      "tableCell");
   AddFrameTypeInfo(nsGkAtoms::bcTableCellFrame,      "bcCell",    "bcTableCell");
   AddFrameTypeInfo(nsGkAtoms::tableColFrame,         "col",       "tableCol");
   AddFrameTypeInfo(nsGkAtoms::tableColGroupFrame,    "colG",      "tableColGroup");
   AddFrameTypeInfo(nsGkAtoms::tableFrame,            "tbl",       "table");
   AddFrameTypeInfo(nsGkAtoms::tableOuterFrame,       "tblO",      "tableOuter");
   AddFrameTypeInfo(nsGkAtoms::tableRowGroupFrame,    "rowG",      "tableRowGroup");
   AddFrameTypeInfo(nsGkAtoms::tableRowFrame,         "row",       "tableRow");

--- a/layout/generic/nsIFrame.h
+++ b/layout/generic/nsIFrame.h
@@ -2867,16 +2867,21 @@ NS_PTR_TO_INT32(frame->Properties().Get(
    * Is this a flex item? (i.e. a non-abs-pos child of a flex container)
    */
   inline bool IsFlexItem() const;
   /**
    * Is this a flex or grid item? (i.e. a non-abs-pos child of a flex/grid container)
    */
   inline bool IsFlexOrGridItem() const;
 
+  /**
+   * @return true if this frame is used as a table caption.
+   */
+  inline bool IsTableCaption() const;
+
   inline bool IsBlockInside() const;
   inline bool IsBlockOutside() const;
   inline bool IsInlineOutside() const;
   inline uint8_t GetDisplay() const;
   inline bool IsFloating() const;
   inline bool IsPositioned() const;
   inline bool IsRelativelyPositioned() const;
   inline bool IsAbsolutelyPositioned() const;

--- a/layout/generic/nsIFrameInlines.h
+++ b/layout/generic/nsIFrameInlines.h
@@ -4,16 +4,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef nsIFrameInlines_h___
 #define nsIFrameInlines_h___
 
 #include "nsContainerFrame.h"
 #include "nsStyleStructInlines.h"
+#include "nsCSSAnonBoxes.h"
 
 bool
 nsIFrame::IsFlexItem() const
 {
   return GetParent() &&
     GetParent()->GetType() == nsGkAtoms::flexContainerFrame &&
     !(GetStateBits() & NS_FRAME_OUT_OF_FLOW);
 }
@@ -26,16 +27,23 @@ nsIFrame::IsFlexOrGridItem() const
     return (t == nsGkAtoms::flexContainerFrame ||
             t == nsGkAtoms::gridContainerFrame) &&
       !(GetStateBits() & NS_FRAME_OUT_OF_FLOW);
   }
   return false;
 }
 
 bool
+nsIFrame::IsTableCaption() const
+{
+  return StyleDisplay()->mDisplay == NS_STYLE_DISPLAY_TABLE_CAPTION &&
+    GetParent()->StyleContext()->GetPseudo() == nsCSSAnonBoxes::tableOuter;
+}
+
+bool
 nsIFrame::IsFloating() const
 {
   return StyleDisplay()->IsFloating(this);
 }
 
 bool
 nsIFrame::IsPositioned() const
 {

--- a/layout/tables/nsTableOuterFrame.cpp
+++ b/layout/tables/nsTableOuterFrame.cpp
@@ -16,16 +16,17 @@
 #include "prinrval.h"
 #include "nsGkAtoms.h"
 #include "nsHTMLParts.h"
 #include "nsIPresShell.h"
 #include "nsIServiceManager.h"
 #include "nsIDOMNode.h"
 #include "nsDisplayList.h"
 #include "nsLayoutUtils.h"
+#include "nsIFrameInlines.h"
 #include <algorithm>
 
 using namespace mozilla;
 using namespace mozilla::layout;
 
 #define NO_SIDE 100
 
 /* virtual */ nscoord
@@ -111,17 +112,17 @@ nsTableOuterFrame::SetInitialChildList(C
 void
 nsTableOuterFrame::AppendFrames(ChildListID     aListID,
                                 nsFrameList&    aFrameList)
 {
   // We only have two child frames: the inner table and a caption frame.
   // The inner frame is provided when we're initialized, and it cannot change
   MOZ_ASSERT(kCaptionList == aListID, "unexpected child list");
   MOZ_ASSERT(aFrameList.IsEmpty() ||
-             aFrameList.FirstChild()->GetType() == nsGkAtoms::tableCaptionFrame,
+             aFrameList.FirstChild()->IsTableCaption(),
              "appending non-caption frame to captionList");
   mCaptionFrames.AppendFrames(this, aFrameList);
 
   // Reflow the new caption frame. It's already marked dirty, so
   // just tell the pres shell.
   PresContext()->PresShell()->
     FrameNeedsReflow(this, nsIPresShell::eTreeChange,
                      NS_FRAME_HAS_DIRTY_CHILDREN);
@@ -129,17 +130,17 @@ nsTableOuterFrame::AppendFrames(ChildLis
 
 void
 nsTableOuterFrame::InsertFrames(ChildListID     aListID,
                                 nsIFrame*       aPrevFrame,
                                 nsFrameList&    aFrameList)
 {
   MOZ_ASSERT(kCaptionList == aListID, "unexpected child list");
   MOZ_ASSERT(aFrameList.IsEmpty() ||
-             aFrameList.FirstChild()->GetType() == nsGkAtoms::tableCaptionFrame,
+             aFrameList.FirstChild()->IsTableCaption(),
              "inserting non-caption frame into captionList");
   MOZ_ASSERT(!aPrevFrame || aPrevFrame->GetParent() == this,
              "inserting after sibling frame with different parent");
   mCaptionFrames.InsertFrames(nullptr, aPrevFrame, aFrameList);
 
   // Reflow the new caption frame. It's already marked dirty, so
   // just tell the pres shell.
   PresContext()->PresShell()->