Change PaintLayer::m_layoutObject to a reference.

third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.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 130 matching lines @@
   void updateRootLayerPosition();
 
   // If the root scroller isn't the root layer then the PaintLayerCompositor
   // must disable clipping on its layers so that the root scroller can
   // expand/shrink its clipping layer in response to browser controls and have
   // the result be visible.
   void updateClippingOnCompositorLayers();
 
   void setIsInWindow(bool);
 
-  static PaintLayerCompositor* frameContentsCompositor(LayoutPart*);
+  static PaintLayerCompositor* frameContentsCompositor(LayoutPart&);
   // Return true if the layers changed.
-  static bool attachFrameContentLayersToIframeLayer(LayoutPart*);
+  static bool attachFrameContentLayersToIframeLayer(LayoutPart&);
 
   // Update the geometry of the layers used for clipping and scrolling in
   // frames.
   void frameViewDidChangeLocation(const IntPoint& contentsOffset);
   void frameViewDidChangeSize();
   void frameViewDidScroll();
   void frameViewScrollbarsExistenceDidChange();
   void rootFixedBackgroundsChanged();
 
   bool scrollingLayerDidChange(PaintLayer*);
@@ skipping 113 matching lines @@
 
   // Layers for overflow controls
   std::unique_ptr<GraphicsLayer> m_layerForHorizontalScrollbar;
   std::unique_ptr<GraphicsLayer> m_layerForVerticalScrollbar;
   std::unique_ptr<GraphicsLayer> m_layerForScrollCorner;
 };
 
 }  // namespace blink
 
 #endif  // PaintLayerCompositor_h