ui/gfx: Make gfx::Canvas inherit from gfx::CanvasSkia.

ui/aura/window_delegate.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 UI_AURA_WINDOW_DELEGATE_H_
 #define UI_AURA_WINDOW_DELEGATE_H_
 #pragma once
 
 #include "ui/aura/aura_export.h"
 #include "ui/base/events.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace gfx {
-class Canvas;
+class CanvasSkia;
 class Point;
 class Rect;
 class Size;
 }
 
 namespace aura {
 
 class Event;
 class GestureEvent;
 class KeyEvent;
@@ skipping 30 matching lines @@
 
   virtual ui::GestureStatus OnGestureEvent(GestureEvent* event) = 0;
 
   // Returns true of the window can be focused.
   virtual bool CanFocus() = 0;
 
   // Invoked when mouse capture is lost on the window.
   virtual void OnCaptureLost() = 0;
 
   // Asks the delegate to paint window contents into the supplied canvas.
-  virtual void OnPaint(gfx::Canvas* canvas) = 0;
+  virtual void OnPaint(gfx::CanvasSkia* canvas) = 0;
 
   // Called from Window's destructor before OnWindowDestroyed and before the
   // children have been destroyed and the window has been removed from its
   // parent.
   virtual void OnWindowDestroying() = 0;
 
   // Called when the Window has been destroyed (i.e. from its destructor). This
   // is called after OnWindowDestroying and after the children have been
   // deleted and the window has been removed from its parent.
   // The delegate can use this as an opportunity to delete itself if necessary.
   virtual void OnWindowDestroyed() = 0;
 
   // Called when the visibility of a Window changed.
   virtual void OnWindowVisibilityChanged(bool visible) = 0;
 
  protected:
   virtual ~WindowDelegate() {}
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_DELEGATE_H_