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 33fd2adcb9183feacc52e1ee0574986e39b1e8cb..928ab73fdf21307c435c5cca3e41956d435cbc19 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -604,7 +604,7 @@ 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)
@@ -722,6 +722,9 @@ public:
     bool adjustForForceCompositedScrollingMode(bool) const;
     bool needsCompositedScrolling() const;
     bool needsToBeStackingContainer() const;
+
+    bool hasScrollParent() const;
+
     bool needsCompositingLayersRebuiltForClip(const RenderStyle* oldStyle, const RenderStyle* newStyle) const;
     bool needsCompositingLayersRebuiltForOverflow(const RenderStyle* oldStyle, const RenderStyle* newStyle) const;
     bool needsCompositingLayersRebuiltForFilters(const RenderStyle* oldStyle, const RenderStyle* newStyle, bool didPaintWithFilters) const;
@@ -1002,6 +1005,7 @@ private:
 
 public:
     GraphicsLayer* layerForScrolling() const;
+    GraphicsLayer* layerForScrollChild() const;
     GraphicsLayer* layerForHorizontalScrollbar() const;
     GraphicsLayer* layerForVerticalScrollbar() const;
     GraphicsLayer* layerForScrollCorner() const;