Add Blink-side flag for enabling/disabling layer squashing.

Source/core/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 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 255 matching lines @@
     }
 
     if (hasAcceleratedCompositing != m_hasAcceleratedCompositing || showRepaintCounter != m_showRepaintCounter || forceCompositingMode != m_forceCompositingMode)
         setCompositingLayersNeedRebuild();
 
     m_hasAcceleratedCompositing = hasAcceleratedCompositing;
     m_showRepaintCounter = showRepaintCounter;
     m_forceCompositingMode = forceCompositingMode;
 }
 
+bool RenderLayerCompositor::isLayerSquashingEnabled() const
+{
+    if (Settings* settings = m_renderView->document().settings())
+        return settings->isLayerSquashingEnabled();
+
+    return false;
+}
+
 bool RenderLayerCompositor::canRender3DTransforms() const
 {
     return hasAcceleratedCompositing() && (m_compositingTriggers & ChromeClient::ThreeDTransformTrigger);
 }
 
 void RenderLayerCompositor::setCompositingLayersNeedRebuild(bool needRebuild)
 {
     if (inCompositingMode())
         m_compositingLayersNeedRebuild = needRebuild;
 }
@@ skipping 2168 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore