Use a boolean hasCompositedLayerMapping() accessor instead of the pointer

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 2059 matching lines @@
 }
 
 bool FrameView::isTransparent() const
 {
     return m_isTransparent;
 }
 
 void FrameView::setTransparent(bool isTransparent)
 {
     m_isTransparent = isTransparent;
-    if (renderView() && renderView()->layer()->compositedLayerMapping())
+    if (renderView() && renderView()->layer()->hasCompositedLayerMapping())
         renderView()->layer()->compositedLayerMapping()->updateContentsOpaque();
 }
 
 bool FrameView::hasOpaqueBackground() const
 {
     return !m_isTransparent && !m_baseBackgroundColor.hasAlpha();
 }
 
 Color FrameView::baseBackgroundColor() const
 {
@@ skipping 1401 matching lines @@
 void FrameView::setLayoutSizeInternal(const IntSize& size)
 {
     if (m_layoutSize == size)
         return;
 
     m_layoutSize = size;
     contentsResized();
 }
 
 } // namespace WebCore