Set up clip and scroll parents on the blink side.

Source/core/rendering/RenderLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 392 matching lines @@
     void scrollRectToVisible(const LayoutRect&, const ScrollAlignment& alignX, const ScrollAlignment& alignY);
 
     LayoutRect getRectToExpose(const LayoutRect& visibleRect, const LayoutRect& exposeRect, const ScrollAlignment& alignX, const ScrollAlignment& alignY);
 
     bool hasHorizontalScrollbar() const { return horizontalScrollbar(); }
     bool hasVerticalScrollbar() const { return verticalScrollbar(); }
 
     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;
     bool hitTestOverflowControls(HitTestResult&, const IntPoint& localPoint);
     IntSize offsetFromResizeCorner(const IntPoint& absolutePoint) const;
 
     void paintOverflowControls(GraphicsContext*, const IntPoint&, const IntRect& damageRect, bool paintingOverlayControls = false);
     void paintScrollCorner(GraphicsContext*, const IntPoint&, const IntRect& damageRect);
     void paintResizer(GraphicsContext*, const IntPoint&, const IntRect& damageRect);
 
@@ skipping 180 matching lines @@
     // paints the layers that intersect the damage rect from back to
     // front.  The hitTest method looks for mouse events by walking
     // layers that intersect the point from front to back.
     void paint(GraphicsContext*, const LayoutRect& damageRect, PaintBehavior = PaintBehaviorNormal, RenderObject* paintingRoot = 0,
         RenderRegion* = 0, PaintLayerFlags = 0);
     bool hitTest(const HitTestRequest&, HitTestResult&);
     bool hitTest(const HitTestRequest&, const HitTestLocation&, HitTestResult&);
     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
     // |rootLayer}.  It also computes our background and foreground clip rects
     // for painting/event handling.
     // Pass offsetFromRoot if known.
     void calculateRects(const ClipRectsContext&, const LayoutRect& paintDirtyRect, LayoutRect& layerBounds,
         ClipRect& backgroundRect, ClipRect& foregroundRect, ClipRect& outlineRect, const LayoutPoint* offsetFromRoot = 0) const;
 
     // Compute and cache clip rects computed with the given layer as the root
@@ skipping 150 matching lines @@
         NotCompositedForNonViewContainer,
         NotCompositedForNoVisibleContent,
         NotCompositedForUnscrollableAncestors,
     };
 
     void setViewportConstrainedNotCompositedReason(ViewportConstrainedNotCompositedReason reason) { m_compositingProperties.viewportConstrainedNotCompositedReason = reason; }
     ViewportConstrainedNotCompositedReason viewportConstrainedNotCompositedReason() const { return static_cast<ViewportConstrainedNotCompositedReason>(m_compositingProperties.viewportConstrainedNotCompositedReason); }
 
     bool isOutOfFlowRenderFlowThread() const { return renderer()->isOutOfFlowRenderFlowThread(); }
 
+    GraphicsLayer* layerForScrollChild() const;
     enum PaintOrderListType {BeforePromote, AfterPromote};
     void computePaintOrderList(PaintOrderListType type, Vector<RefPtr<Node> >&);
     bool scrollsWithRespectTo(const RenderLayer*) const;
 
     enum ForceNeedsCompositedScrollingMode {
         DoNotForceCompositedScrolling = 0,
         CompositedScrollingAlwaysOn = 1,
         CompositedScrollingAlwaysOff = 2
     };
 
@@ skipping 523 matching lines @@
 
 } // namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const WebCore::RenderLayer*);
 void showLayerTree(const WebCore::RenderObject*);
 #endif
 
 #endif // RenderLayer_h