Made root translation layer the root when using pinch virtual viewport.

Source/core/rendering/compositing/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 174 matching lines @@
 
     // Whether the layer could ever be composited.
     bool canBeComposited(const RenderLayer*) const;
 
     // FIXME: Move allocateOrClearCompositedLayerMapping to CompositingLayerAssigner once we've fixed
     // the compositing chicken/egg issues.
     bool allocateOrClearCompositedLayerMapping(RenderLayer*, CompositingStateTransitionType compositedLayerUpdate);
 
     void updateDirectCompositingReasons(RenderLayer*);
 
+    void setOverlayLayer(GraphicsLayer*);
+
 private:
     class OverlapMap;
 
     void assertNoUnresolvedDirtyBits();
 
     // Make updates to the layer based on viewport-constrained properties such as position:fixed. This can in turn affect
     // compositing.
     bool updateLayerIfViewportConstrained(RenderLayer*);
 
     // GraphicsLayerClient implementation
@@ skipping 82 matching lines @@
     OwnPtr<GraphicsLayer> m_layerForVerticalScrollbar;
     OwnPtr<GraphicsLayer> m_layerForScrollCorner;
 #if USE(RUBBER_BANDING)
     OwnPtr<GraphicsLayer> m_layerForOverhangShadow;
 #endif
 };
 
 } // namespace WebCore
 
 #endif // RenderLayerCompositor_h