Revert 114283 - Avoid using backing store for compositing layers that just need to clip

Source/WebCore/rendering/RenderLayerCompositor.h

 /*
  * Copyright (C) 2009 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 117 matching lines @@
     // Notify us that a layer has been added or removed
     void layerWasAdded(RenderLayer* parent, RenderLayer* child);
     void layerWillBeRemoved(RenderLayer* parent, RenderLayer* child);
 
     // Get the nearest ancestor layer that has overflow or clip, but is not a stacking context
     RenderLayer* enclosingNonStackingClippingLayer(const RenderLayer* layer) const;
 
     // Repaint parts of all composited layers that intersect the given absolute rectangle.
     void repaintCompositedLayersAbsoluteRect(const IntRect&);
 
-    // Returns true if the given layer needs it own backing store.
-    bool requiresOwnBackingStore(const RenderLayer*, const RenderLayer* compositingAncestorLayer) const;
-
     RenderLayer* rootRenderLayer() const;
     GraphicsLayer* rootGraphicsLayer() const;
     GraphicsLayer* scrollLayer() const;
 
     enum RootLayerAttachment {
         RootLayerUnattached,
         RootLayerAttachedViaChromeClient,
         RootLayerAttachedViaEnclosingFrame
     };
 
@@ skipping 201 matching lines @@
     int m_secondaryCompositedLayerCount; // count of layers that have to be composited because of stacking or overlap.
     double m_obligatoryBackingAreaMegaPixels;
     double m_secondaryBackingAreaMegaPixels;
 #endif
 };
 
 
 } // namespace WebCore
 
 #endif // RenderLayerCompositor_h