Continuation of CL 5685007, rename the singleton accessor method in more files.

chrome/browser/chromeos/volume_bubble.h

 // Copyright (c) 2010 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 CHROME_BROWSER_CHROMEOS_VOLUME_BUBBLE_H_
 #define CHROME_BROWSER_CHROMEOS_VOLUME_BUBBLE_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "chrome/browser/chromeos/setting_level_bubble.h"
 
 template <typename T> struct DefaultSingletonTraits;
 
 namespace chromeos {
 
 // Singleton class controlling volume bubble.
 class VolumeBubble : public SettingLevelBubble {
  public:
-  static VolumeBubble* instance();
+  static VolumeBubble* GetInstance();
 
  private:
   friend struct DefaultSingletonTraits<VolumeBubble>;
 
   VolumeBubble();
   virtual ~VolumeBubble() {}
 
   DISALLOW_COPY_AND_ASSIGN(VolumeBubble);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_VOLUME_BUBBLE_H_