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

ui/views/controls/scrollbar/base_scroll_bar_thumb.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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_VIEWS_CONTROLS_SCROLLBAR_BASE_SCROLL_BAR_THUMB_H_
 #define UI_VIEWS_CONTROLS_SCROLLBAR_BASE_SCROLL_BAR_THUMB_H_
 #pragma once
 
 #include "ui/gfx/size.h"
 #include "ui/views/controls/button/custom_button.h"
 #include "ui/views/controls/scrollbar/scroll_bar.h"
 #include "ui/views/view.h"
 
 namespace gfx {
-class Canvas;
+class CanvasSkia;
 }
 
 namespace views {
 
 class BaseScrollBar;
 
 ///////////////////////////////////////////////////////////////////////////////
 //
 // BaseScrollBarThumb
 //
@@ skipping 16 matching lines @@
   void SetPosition(int position);
 
   // Gets the position of the thumb on the x or y axis.
   int GetPosition() const;
 
   // View overrides:
   virtual gfx::Size GetPreferredSize() OVERRIDE = 0;
 
  protected:
   // View overrides:
-  virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE = 0;
+  virtual void OnPaint(gfx::CanvasSkia* canvas) OVERRIDE = 0;
   virtual void OnMouseEntered(const MouseEvent& event) OVERRIDE;
   virtual void OnMouseExited(const MouseEvent& event) OVERRIDE;
   virtual bool OnMousePressed(const MouseEvent& event) OVERRIDE;
   virtual bool OnMouseDragged(const MouseEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const MouseEvent& event) OVERRIDE;
   virtual void OnMouseCaptureLost() OVERRIDE;
 
   CustomButton::ButtonState GetState() const;
   // Update our state and schedule a repaint when the mouse moves over us.
   void SetState(CustomButton::ButtonState state);
@@ skipping 10 matching lines @@
 
   // The current state of the thumb button.
   CustomButton::ButtonState state_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseScrollBarThumb);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_SCROLLBAR_BASE_SCROLL_BAR_THUMB_H_