Refactor the PlatformContext layer to have only one class.

views/window/window_win.cc

 // Copyright (c) 2006-2008 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 "views/window/window_win.h"
 
 #include <shellapi.h>
 
-#include "app/gfx/canvas.h"
+#include "app/gfx/canvas_paint.h"
 #include "app/gfx/font.h"
 #include "app/gfx/icon_util.h"
 #include "app/gfx/path.h"
 #include "app/l10n_util.h"
 #include "app/resource_bundle.h"
 #include "app/theme_provider.h"
 #include "app/win_util.h"
 #include "base/win_util.h"
 #include "views/widget/root_view.h"
 #include "views/window/client_view.h"
@@ skipping 1409 matching lines @@
   }
   return TRUE;
 }
 }  // namespace
 
 void Window::CloseAllSecondaryWindows() {
   EnumThreadWindows(GetCurrentThreadId(), WindowCallbackProc, 0);
 }
 
 }  // namespace views