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

ash/system/tray_user.cc

 // 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.
 
 #include "ash/system/tray_user.h"
 
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "base/utf_string_conversions.h"
 #include "grit/ash_strings.h"
@@ skipping 31 matching lines @@
   virtual void OnMouseEntered(const views::MouseEvent& event) OVERRIDE {
     hover_ = true;
     SchedulePaint();
   }
 
   virtual void OnMouseExited(const views::MouseEvent& event) OVERRIDE {
     hover_ = false;
     SchedulePaint();
   }
 
-  virtual void OnPaintBackground(gfx::Canvas* canvas) OVERRIDE {
+  virtual void OnPaintBackground(gfx::CanvasSkia* canvas) OVERRIDE {
     if (hover_)
       hover_bg_->Paint(canvas, this);
     else
       views::TextButton::OnPaintBackground(canvas);
   }
 
   bool hover_;
   views::Background* hover_bg_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayButton);
@@ skipping 101 matching lines @@
 }
 
 void TrayUser::DestroyDefaultView() {
 }
 
 void TrayUser::DestroyDetailedView() {
 }
 
 }  // namespace internal
 }  // namespace ash