RenderLayer::scrollParent should walk the containing block chain

Source/core/rendering/compositing/CompositedLayerMapping.cpp

Index: Source/core/rendering/compositing/CompositedLayerMapping.cpp
diff --git a/Source/core/rendering/compositing/CompositedLayerMapping.cpp b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
index 8f2e9dd6ff369c2585001b7e05878d9b85d121a5..264e6375043d4f8c84e15844fb608e4324820757 100644
--- a/Source/core/rendering/compositing/CompositedLayerMapping.cpp
+++ b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
@@ -380,7 +380,7 @@ bool CompositedLayerMapping::updateGraphicsLayerConfiguration(GraphicsLayerUpdat
     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;
     }