Use a boolean hasCompositedLayerMapping() accessor instead of the pointer

Source/core/rendering/RenderLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. 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>
@@ skipping 27 matching lines @@
  * version of this file under the LGPL, indicate your decision by
  * deletingthe provisions above and replace them with the notice and
  * other provisions required by the MPL or the GPL, as the case may be.
  * If you do not delete the provisions above, a recipient may use your
  * version of this file under any of the LGPL, the MPL or the GPL.
  */
 
 #ifndef RenderLayer_h
 #define RenderLayer_h
 
+#include "core/rendering/CompositedLayerMappingPtr.h"
 #include "core/rendering/CompositingReasons.h"
 #include "core/rendering/LayerPaintingInfo.h"
 #include "core/rendering/PaintInfo.h"
 #include "core/rendering/RenderBox.h"
 #include "core/rendering/RenderLayerClipper.h"
 #include "core/rendering/RenderLayerReflectionInfo.h"
 #include "core/rendering/RenderLayerRepainter.h"
 #include "core/rendering/RenderLayerScrollableArea.h"
 #include "core/rendering/RenderLayerStackingNode.h"
 
@@ skipping 280 matching lines @@
 
     bool hasBlendMode() const;
     bool paintsWithBlendMode() const { return hasBlendMode() && compositingState() != PaintsIntoOwnBacking; }
 
     void* operator new(size_t);
     // Only safe to call from RenderLayerModelObject::destroyLayer()
     void operator delete(void*);
 
     CompositingState compositingState() const;
 
-    // NOTE: If you are accessing the CompositedLayerMapping as a boolean condition to determine the state of compositing for this layer,
+    CompositedLayerMappingPtr compositedLayerMapping() const { return m_compositedLayerMapping.get(); }
+    CompositedLayerMappingPtr ensureCompositedLayerMapping();
+
+    // NOTE: If you are using hasCompositedLayerMapping to determine the state of compositing for this layer,
+    // (and not just to do bookkeeping related to the mapping like, say, allocating or deallocating a mapping),
     // then you may have incorrect logic. Use compositingState() instead.
-    CompositedLayerMapping* compositedLayerMapping() const { return m_compositedLayerMapping.get(); }
-    CompositedLayerMapping* ensureCompositedLayerMapping();
+    bool hasCompositedLayerMapping() const { return m_compositedLayerMapping.get(); }
     void clearCompositedLayerMapping(bool layerBeingDestroyed = false);
 
     bool hasCompositedMask() const;
     bool hasCompositedClippingMask() const;
     bool needsCompositedScrolling() const { return m_scrollableArea && m_scrollableArea->needsCompositedScrolling(); }
 
     RenderLayer* scrollParent() const;
     RenderLayer* clipParent() const;
 
     bool needsCompositingLayersRebuiltForClip(const RenderStyle* oldStyle, const RenderStyle* newStyle) const;
@@ skipping 369 matching lines @@
 
 } // namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const WebCore::RenderLayer*);
 void showLayerTree(const WebCore::RenderObject*);
 #endif
 
 #endif // RenderLayer_h