Set up clip and scroll parents on the blink side.

Source/core/rendering/RenderLayer.h

Index: Source/core/rendering/RenderLayer.h
diff --git a/Source/core/rendering/RenderLayer.h b/Source/core/rendering/RenderLayer.h
index a3374934820fd4c057d3af5c8b0cd49d257617e1..680fe297847030d7680093649a3fbcf178a5a1c9 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -420,6 +420,7 @@ public:
     int verticalScrollbarWidth(OverlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize) const;
     int horizontalScrollbarHeight(OverlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize) const;
 
+    bool hasScrollParent() const { return m_compositingProperties.compositingReasons & CompositingReasonOverflowScrollingParent; }
     // isPointInResizeControl() is used for testing if a pointer/touch position is in the resize control
     // area.
     bool isPointInResizeControl(const IntPoint& absolutePoint, ResizerHitTestType resizerHitTestType) const;
@@ -620,18 +621,20 @@ public:
     void paintOverlayScrollbars(GraphicsContext*, const LayoutRect& damageRect, PaintBehavior, RenderObject* paintingRoot = 0);
 
     struct ClipRectsContext {
-        ClipRectsContext(const RenderLayer* inRootLayer, RenderRegion* inRegion, ClipRectsType inClipRectsType, OverlayScrollbarSizeRelevancy inOverlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize, ShouldRespectOverflowClip inRespectOverflowClip = RespectOverflowClip)
+        ClipRectsContext(const RenderLayer* inRootLayer, RenderRegion* inRegion, ClipRectsType inClipRectsType, OverlayScrollbarSizeRelevancy inOverlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize, ShouldRespectOverflowClip inRespectOverflowClip = RespectOverflowClip, const RenderLayer* scrollParent = 0)
             : rootLayer(inRootLayer)
             , region(inRegion)
             , clipRectsType(inClipRectsType)
             , overlayScrollbarSizeRelevancy(inOverlayScrollbarSizeRelevancy)
             , respectOverflowClip(inRespectOverflowClip)
+            , scrollParent(scrollParent)
         { }
         const RenderLayer* rootLayer;
         RenderRegion* region;
         ClipRectsType clipRectsType;
         OverlayScrollbarSizeRelevancy overlayScrollbarSizeRelevancy;
         ShouldRespectOverflowClip respectOverflowClip;
+        const RenderLayer* scrollParent;
     };
 
     // This method figures out our layerBounds in coordinates relative to
@@ -807,6 +810,7 @@ public:
 
     bool isOutOfFlowRenderFlowThread() const { return renderer()->isOutOfFlowRenderFlowThread(); }
 
+    GraphicsLayer* layerForScrollChild() const;
     enum PaintOrderListType {BeforePromote, AfterPromote};
     void computePaintOrderList(PaintOrderListType type, Vector<RefPtr<Node> >&);