Simplify platform_canvas.h by recognizing that PlatformCanvas does not actually extend

webkit/plugins/ppapi/mock_platform_image_2d.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WEBKIT_PLUGINS_PPAPI_MOCK_PLATFORM_IMAGE_2D_H_
 #define WEBKIT_PLUGINS_PPAPI_MOCK_PLATFORM_IMAGE_2D_H_
 
 #include "webkit/plugins/ppapi/plugin_delegate.h"
+#include "skia/ext/platform_canvas.h"
 
 namespace webkit {
 namespace ppapi {
 
 class MockPlatformImage2D : public PluginDelegate::PlatformImage2D {
  public:
   MockPlatformImage2D(int width, int height);
   virtual ~MockPlatformImage2D();
 
   // PlatformImage2D implementation.
   virtual skia::PlatformCanvas* Map() OVERRIDE;
   virtual intptr_t GetSharedMemoryHandle(uint32* byte_count) const OVERRIDE;
   virtual TransportDIB* GetTransportDIB() const OVERRIDE;
 
  private:
   int width_;
   int height_;
 };
 
 }  // namespace ppapi
 }  // namespace webkit
 
 #endif  // WEBKIT_PLUGINS_PPAPI_MOCK_PLATFORM_IMAGE_2D_H_