RenderLayer::scrollParent should walk the containing block chain

Source/core/rendering/compositing/CompositedLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 362 matching lines @@
 
     // Our scrolling layer will clip.
     if (m_owningLayer.needsCompositedScrolling())
         needsDescendantsClippingLayer = false;
 
     RenderLayer* scrollParent = compositor->acceleratedCompositingForOverflowScrollEnabled() ? m_owningLayer.scrollParent() : 0;
     bool needsAncestorClip = compositor->clippedByNonAncestorInStackingTree(&m_owningLayer);
     if (scrollParent) {
         // If our containing block is our ancestor scrolling layer, then we'll already be clipped
         // to it via our scroll parent and we don't need an ancestor clipping layer.
-        if (m_owningLayer.renderer()->containingBlock()->enclosingLayer() == m_owningLayer.ancestorCompositedScrollingLayer())
+        if (m_owningLayer.renderer()->containingBlock()->enclosingLayer() == m_owningLayer.ancestorScrollingLayer())
             needsAncestorClip = false;
     }
 
     if (updateClippingLayers(needsAncestorClip, needsDescendantsClippingLayer))
         layerConfigChanged = true;
 
     if (updateOverflowControlsLayers(requiresHorizontalScrollbarLayer(), requiresVerticalScrollbarLayer(), requiresScrollCornerLayer()))
         layerConfigChanged = true;
 
     bool scrollingConfigChanged = false;
@@ skipping 1872 matching lines @@
     } else if (graphicsLayer == m_scrollingBlockSelectionLayer.get()) {
         name = "Scrolling Block Selection Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore