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

webkit/tools/test_shell/webwidget_host_win.cc

 // Copyright (c) 2011 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/tools/test_shell/webwidget_host.h"
 
 #include "base/logging.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPopupMenu.h"
@@ skipping 221 matching lines @@
 
 void WebWidgetHost::Paint() {
   RECT r;
   GetClientRect(view_, &r);
   gfx::Rect client_rect(r);
 
   // Allocate a canvas if necessary
   if (!canvas_.get()) {
     ResetScrollRect();
     paint_rect_ = client_rect;
-    canvas_.reset(new skia::PlatformCanvas(
+    canvas_.reset(skia::CreatePlatformCanvas(
         paint_rect_.width(), paint_rect_.height(), true));
   }
 
   webwidget_->animate(0.0);
 
   // This may result in more invalidation
   webwidget_->layout();
 
   // Scroll the canvas if necessary
   scroll_rect_.Intersect(client_rect);
@@ skipping 120 matching lines @@
 void WebWidgetHost::PaintRect(const gfx::Rect& rect) {
 #ifndef NDEBUG
   DCHECK(!painting_);
 #endif
   DCHECK(canvas_.get());
 
   set_painting(true);
   webwidget_->paint(canvas_.get(), rect);
   set_painting(false);
 }