Delete the Layer Squashing runtime feature.

Source/web/WebRuntimeFeatures.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 255 matching lines @@
 void WebRuntimeFeatures::enableSharedWorker(bool enable)
 {
     RuntimeEnabledFeatures::setSharedWorkerEnabled(enable);
 }
 
 void WebRuntimeFeatures::enablePreciseMemoryInfo(bool enable)
 {
     RuntimeEnabledFeatures::setPreciseMemoryInfoEnabled(enable);
 }
 
-void WebRuntimeFeatures::enableLayerSquashing(bool enable)
-{
-    RuntimeEnabledFeatures::setLayerSquashingEnabled(enable);
-}
-
 void WebRuntimeFeatures::enableShowModalDialog(bool enable)
 {
     RuntimeEnabledFeatures::setShowModalDialogEnabled(enable);
 }
 
 void WebRuntimeFeatures::enableLaxMixedContentChecking(bool enable)
 {
     RuntimeEnabledFeatures::setLaxMixedContentCheckingEnabled(enable);
 }
 
@@ skipping 21 matching lines @@
 {
     RuntimeEnabledFeatures::setSVG1DOMEnabled(enable);
 }
 
 void WebRuntimeFeatures::enableReducedReferrerGranularity(bool enable)
 {
     RuntimeEnabledFeatures::setReducedReferrerGranularityEnabled(enable);
 }
 
 } // namespace blink