Bug 946502. Part 4: Remove mStickyPosFrame. r=mattwoodrow

--HG--
extra : rebase_source : 71bcbd246cf6806196a3e64d32fdde169bddfa07

layout/base/nsDisplayList.cpp

@@ -3417,10 +3417,9 @@ nsDisplayResolution::BuildLayer(nsDisplayListBuilder* aBuilder,
 
 nsDisplayStickyPosition::nsDisplayStickyPosition(nsDisplayListBuilder* aBuilder,
                                                  nsIFrame* aFrame,
-                                                 nsIFrame* aStickyPosFrame,
                                                  nsDisplayList* aList)
   : nsDisplayOwnLayer(aBuilder, aFrame, aList)
-  , mStickyPosFrame(aStickyPosFrame) {
+{
   MOZ_COUNT_CTOR(nsDisplayStickyPosition);
 }
 
@@ -3457,7 +3456,7 @@ nsDisplayStickyPosition::BuildLayer(nsDisplayListBuilder* aBuilder,
 
   nsLayoutUtils::SetFixedPositionLayerData(layer, scrollFrame,
     nsRect(scrollFrame->GetOffsetToCrossDoc(ReferenceFrame()), scrollFrameSize),
-    mStickyPosFrame, presContext, aContainerParameters);
+    mFrame, presContext, aContainerParameters);
 
   ViewID scrollId = nsLayoutUtils::FindOrCreateIDFor(
     stickyScrollContainer->ScrollFrame()->GetScrolledFrame()->GetContent());
@@ -3492,7 +3491,7 @@ bool nsDisplayStickyPosition::TryMerge(nsDisplayListBuilder* aBuilder, nsDisplay
     return false;
   // Items with the same fixed position frame can be merged.
   nsDisplayStickyPosition* other = static_cast<nsDisplayStickyPosition*>(aItem);
-  if (other->mStickyPosFrame != mStickyPosFrame)
+  if (other->mFrame != mFrame)
     return false;
   if (aItem->GetClip() != GetClip())
     return false;

layout/base/nsDisplayList.h

@@ -2720,7 +2720,7 @@ public:
 class nsDisplayStickyPosition : public nsDisplayOwnLayer {
 public:
   nsDisplayStickyPosition(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
-                          nsIFrame* aStickyPosFrame, nsDisplayList* aList);
+                          nsDisplayList* aList);
 #ifdef NS_BUILD_REFCNT_LOGGING
   virtual ~nsDisplayStickyPosition();
 #endif
@@ -2736,9 +2736,6 @@ public:
     return mozilla::LAYER_ACTIVE;
   }
   virtual bool TryMerge(nsDisplayListBuilder* aBuilder, nsDisplayItem* aItem) MOZ_OVERRIDE;
-
-protected:
-  nsIFrame* mStickyPosFrame;
 };
 
 /**

layout/generic/nsFrame.cpp

@@ -1996,8 +1996,7 @@ nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
    */
   if (useStickyPosition) {
     resultList.AppendNewToTop(
-        new (aBuilder) nsDisplayStickyPosition(aBuilder, this, this,
-                                               &resultList));
+        new (aBuilder) nsDisplayStickyPosition(aBuilder, this, &resultList));
   }
 
   /* If we're going to apply a transformation and don't have preserve-3d set, wrap