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

ui/views/controls/button/image_button.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_BUTTON_IMAGE_BUTTON_H_
 #define UI_VIEWS_CONTROLS_BUTTON_IMAGE_BUTTON_H_
 #pragma once
 
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/views/controls/button/custom_button.h"
 
@@ skipping 25 matching lines @@
   enum VerticalAlignment { ALIGN_TOP = 0,
                            ALIGN_MIDDLE,
                            ALIGN_BOTTOM };
 
   // Sets how the image is laid out within the button's bounds.
   void SetImageAlignment(HorizontalAlignment h_align,
                          VerticalAlignment v_align);
 
   // Overridden from View:
   virtual gfx::Size GetPreferredSize() OVERRIDE;
-  virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
+  virtual void OnPaint(gfx::CanvasSkia* canvas) OVERRIDE;
 
   // Sets preferred size, so it could be correctly positioned in layout even if
   // it is NULL.
   void SetPreferredSize(const gfx::Size& preferred_size) {
     preferred_size_ = preferred_size;
   }
 
  protected:
   // Returns the image to paint. This is invoked from paint and returns a value
   // from images.
@@ skipping 56 matching lines @@
   // The parent class's tooltip_text_ is displayed when not toggled, and
   // this one is shown when toggled.
   string16 toggled_tooltip_text_;
 
   DISALLOW_COPY_AND_ASSIGN(ToggleImageButton);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_BUTTON_IMAGE_BUTTON_H_