Issue #1355 - Speed up the traversal of a table row frame's child cells

Speed up getting the first cellframe in a row and the next cellframe after the given one

layout/tables/nsTableCellFrame.cpp

@@ -59,20 +59,6 @@ nsTableCellFrame::~nsTableCellFrame()
 
 NS_IMPL_FRAMEARENA_HELPERS(nsTableCellFrame)
 
-nsTableCellFrame*
-nsTableCellFrame::GetNextCell() const
-{
-  nsIFrame* childFrame = GetNextSibling();
-  while (childFrame) {
-    nsTableCellFrame *cellFrame = do_QueryFrame(childFrame);
-    if (cellFrame) {
-      return cellFrame;
-    }
-    childFrame = childFrame->GetNextSibling();
-  }
-  return nullptr;
-}
-
 void
 nsTableCellFrame::Init(nsIContent*       aContent,
                        nsContainerFrame* aParent,

layout/tables/nsTableCellFrame.h

@@ -215,7 +215,17 @@ public:
   bool HasPctOverBSize();
   void SetHasPctOverBSize(bool aValue);
 
-  nsTableCellFrame* GetNextCell() const;
+  nsTableCellFrame* GetNextCell() const
+  {
+    nsIFrame* sibling = GetNextSibling();
+#ifdef DEBUG
+    if (sibling) {
+      nsTableCellFrame* cellFrame = do_QueryFrame(sibling);
+      MOZ_ASSERT(cellFrame, "How do we have a non-cell sibling?");
+    }
+#endif // DEBUG
+    return static_cast<nsTableCellFrame*>(sibling);
+  }
 
   virtual LogicalMargin GetBorderWidth(WritingMode aWM) const;
 
@@ -350,4 +360,17 @@ private:
   BCPixelSize mIStartBorder;
 };
 
+// Implemented here because that's a sane-ish way to make the includes work out.
+inline nsTableCellFrame* nsTableRowFrame::GetFirstCell() const
+{
+  nsIFrame* firstChild = mFrames.FirstChild();
+#ifdef DEBUG
+    if (firstChild) {
+      nsTableCellFrame* cellFrame = do_QueryFrame(firstChild);
+      MOZ_ASSERT(cellFrame, "How do we have a non-cell sibling?");
+    }
+#endif // DEBUG
+  return static_cast<nsTableCellFrame*>(firstChild);
+}
+
 #endif

layout/tables/nsTableRowFrame.cpp

@@ -304,18 +304,6 @@ GetBSizeOfRowsSpannedBelowFirst(nsTableCellFrame& aTableCellFrame,
   return bsize;
 }
 
-nsTableCellFrame*
-nsTableRowFrame::GetFirstCell()
-{
-  for (nsIFrame* childFrame : mFrames) {
-    nsTableCellFrame *cellFrame = do_QueryFrame(childFrame);
-    if (cellFrame) {
-      return cellFrame;
-    }
-  }
-  return nullptr;
-}
-
 /**
  * Post-reflow hook. This is where the table row does its post-processing
  */

layout/tables/nsTableRowFrame.h

@@ -82,7 +82,9 @@ public:
                                 const nsRect&           aDirtyRect,
                                 const nsDisplayListSet& aLists) override;
 
-  nsTableCellFrame* GetFirstCell() ;
+  // Implemented in nsTableCellFrame.h, because it needs to know about the
+  // nsTableCellFrame class, but we can't include nsTableCellFrame.h here.
+  inline nsTableCellFrame* GetFirstCell() const;
 
   /** calls Reflow for all of its child cells.
     * Cells with rowspan=1 are all set to the same height and stacked horizontally.