Add compile flag for enabling the compostior

sky/engine/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 61 matching lines @@
     // composited RenderLayers)
     bool inCompositingMode() const;
     // FIXME: Replace all callers with inCompositingMdoe and remove this function.
     bool staleInCompositingMode() const;
     // This will make a compositing layer at the root automatically, and hook up to
     // the native view/window system.
     void setCompositingModeEnabled(bool);
 
     // Returns true if the accelerated compositing is enabled
     // FIXME(sky): Remove
-    bool hasAcceleratedCompositing() const { return true; }
+    bool hasAcceleratedCompositing() const;
     bool layerSquashingEnabled() const;
 
     bool preferCompositingToLCDTextEnabled() const;
 
     bool rootShouldAlwaysComposite() const;
 
     // Copy the accelerated compositing related flags from Settings
     void updateAcceleratedCompositingSettings();
 
     // Used to indicate that a compositing update will be needed for the next frame that gets drawn.
@@ skipping 117 matching lines @@
     OwnPtr<GraphicsLayer> m_containerLayer;
     OwnPtr<GraphicsLayer> m_scrollLayer;
 
     // Enclosing layer for overflow controls and the clipping layer
     OwnPtr<GraphicsLayer> m_overflowControlsHostLayer;
 };
 
 } // namespace blink
 
 #endif // RenderLayerCompositor_h