Making GraphicsContext the owner of PlatformContext.

Source/core/platform/graphics/chromium/OpaqueRectTrackingContentLayerDelegate.cpp

 /*
  * Copyright (C) 2012 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:
  * 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 33 matching lines @@
     , m_opaque(false)
 {
 }
 
 OpaqueRectTrackingContentLayerDelegate::~OpaqueRectTrackingContentLayerDelegate()
 {
 }
 
 void OpaqueRectTrackingContentLayerDelegate::paintContents(SkCanvas* canvas, const WebRect& clip, bool canPaintLCDText, WebFloatRect& opaque)
 {
-    PlatformContextSkia platformContext(canvas);
-    platformContext.setTrackOpaqueRegion(!m_opaque);
-    platformContext.setDrawingToImageBuffer(!m_opaque);
-    GraphicsContext context(&platformContext);
+    GraphicsContext context(canvas);
+    PlatformContextSkia* platformContext = context.platformContext();
+    platformContext->setTrackOpaqueRegion(!m_opaque);
+    platformContext->setDrawingToImageBuffer(!m_opaque);
     context.setShouldSmoothFonts(canPaintLCDText && m_opaque);
 
     // Record transform prior to painting, as all opaque tracking will be
     // relative to this current value.
     AffineTransform canvasToContentTransform = context.getCTM().inverse();
 
     m_painter->paint(context, clip);
 
     // Transform tracked opaque paints back to our layer's content space.
     ASSERT(canvasToContentTransform.isInvertible());
     ASSERT(canvasToContentTransform.preservesAxisAlignment());
-    opaque = canvasToContentTransform.mapRect(platformContext.opaqueRegion().asRect());
+    opaque = canvasToContentTransform.mapRect(platformContext->opaqueRegion().asRect());
 }
 
 }