Update scroll parent correctly for squashing layers.

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 175 matching lines @@
 
 RenderLayerCompositor* RenderLayer::compositor() const
 {
     if (!renderer()->view())
         return 0;
     return renderer()->view()->compositor();
 }
 
 void RenderLayer::contentChanged(ContentChangeType changeType)
 {
+    // updateLayerCompositingState will query compositingReasons for accelerated overflow scrolling.
+    // This is tripped by LayoutTests/compositing/content-changed-chicken-egg.html
+    DisableCompositingQueryAsserts disabler;
+
     // This can get called when video becomes accelerated, so the layers may change.
     if (changeType == CanvasChanged || changeType == VideoChanged || changeType == FullScreenChanged)
         compositor()->updateLayerCompositingState(this);
 
     if (changeType == CanvasContextChanged)
         compositor()->setNeedsCompositingUpdate(CompositingUpdateAfterCanvasContextChange);
 
     if (m_compositedLayerMapping)
         m_compositedLayerMapping->contentChanged(changeType);
 }
@@ skipping 3864 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif