Disable layer squashing

Source/core/rendering/compositing/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 188 matching lines @@
     // No tests fail if it's deleted.
     if (hasAcceleratedCompositing != m_hasAcceleratedCompositing)
         setCompositingLayersNeedRebuild();
 
     m_hasAcceleratedCompositing = hasAcceleratedCompositing;
     m_rootShouldAlwaysCompositeDirty = true;
 }
 
 bool RenderLayerCompositor::layerSquashingEnabled() const
 {
+    if (!RuntimeEnabledFeatures::layerSquashingEnabled())
+        return false;
     if (Settings* settings = m_renderView.document().settings())
         return settings->layerSquashingEnabled();
     return true;
 }
 
 bool RenderLayerCompositor::legacyOrCurrentAcceleratedCompositingForOverflowScrollEnabled() const
 {
     return legacyAcceleratedCompositingForOverflowScrollEnabled() || acceleratedCompositingForOverflowScrollEnabled();
 }
 
@@ skipping 1496 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "LocalFrame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore