Allow proper highlighting on universal overflow scroll.

Source/core/rendering/compositing/CompositedLayerMapping.h

 /*
  * 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 188 matching lines @@
     LayoutSize contentOffsetInCompositingLayer() const;
 
     LayoutPoint squashingOffsetFromTransformedAncestor()
     {
         return m_squashingLayerOffsetFromTransformedAncestor;
     }
 
     // If there is a squashed layer painting into this CLM that is an ancestor of the given RenderObject, return it. Otherwise return 0.
     const GraphicsLayerPaintInfo* containingSquashedLayer(const RenderObject*);
 
+    void updateScrollingContentsForSelectionGaps(const IntRect& blockSelectionGapsBounds);
+
 private:
     static const GraphicsLayerPaintInfo* containingSquashedLayer(const RenderObject*,  const Vector<GraphicsLayerPaintInfo>& layers);
 
     // Helper methods to updateGraphicsLayerGeometry:
     void computeGraphicsLayerParentLocation(const RenderLayer* compositingContainer, const IntRect& ancestorCompositingBounds, IntPoint& graphicsLayerParentLocation);
     void updateSquashingLayerGeometry(const LayoutPoint& offsetFromCompositedAncestor, const IntPoint& graphicsLayerParentLocation, const RenderLayer& referenceLayer, Vector<GraphicsLayerPaintInfo>& layers, GraphicsLayer*, LayoutPoint* offsetFromTransformedAncestor);
     void updateMainGraphicsLayerGeometry(const IntRect& relativeCompositingBounds, const IntRect& localCompositingBounds, IntPoint& graphicsLayerParentLocation);
     void updateAncestorClippingLayerGeometry(const RenderLayer* compositingContainer, const IntPoint& snappedOffsetFromCompositedAncestor, IntPoint& graphicsLayerParentLocation);
     void updateChildContainmentLayerGeometry(const IntRect& clippingBox, const IntRect& localCompositingBounds);
     void updateChildTransformLayerGeometry();
@@ skipping 172 matching lines @@
     LayoutRect m_compositedBounds;
 
     bool m_artificiallyInflatedBounds : 1; // bounds had to be made non-zero to make transform-origin work
     bool m_isMainFrameRenderViewLayer : 1;
     bool m_requiresOwnBackingStoreForIntrinsicReasons : 1;
     bool m_requiresOwnBackingStoreForAncestorReasons : 1;
     bool m_canCompositeFilters : 1;
     bool m_backgroundLayerPaintsFixedRootBackground : 1;
     bool m_needToUpdateGraphicsLayer : 1;
     bool m_needToUpdateGraphicsLayerOfAllDecendants : 1;
+    bool m_scrollingContentsAreEmpty : 1;
 };
 
 } // namespace WebCore
 
 #endif // CompositedLayerMapping_h