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

webkit/plugins/ppapi/mock_platform_image_2d.cc

 // 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.
 
 #include "webkit/plugins/ppapi/mock_platform_image_2d.h"
 
 #include "skia/ext/platform_canvas.h"
 
 namespace webkit {
 namespace ppapi {
 
 MockPlatformImage2D::MockPlatformImage2D(int width, int height)
   : width_(width),
     height_(height) {
 }
 
 MockPlatformImage2D::~MockPlatformImage2D() {
 }
 
 skia::PlatformCanvas* MockPlatformImage2D::Map() {
-  return new skia::PlatformCanvas(width_, height_, true);
+  return skia::CreatePlatformCanvas(width_, height_, true);
 }
 
 intptr_t MockPlatformImage2D::GetSharedMemoryHandle(uint32* byte_count) const {
   *byte_count = 0;
   return 0;
 }
 
 TransportDIB* MockPlatformImage2D::GetTransportDIB() const {
   return NULL;
 }
 
 }  // namespace ppapi
 }  // namespace webkit