Add a new GetInstance() method for remaining files with singleton classes under chrome/browser.

chrome/browser/chromeos/volume_bubble.cc

 // 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.
 
 #include "chrome/browser/chromeos/volume_bubble.h"
 
 #include "app/resource_bundle.h"
 #include "grit/theme_resources.h"
 
 namespace chromeos {
 
 VolumeBubble::VolumeBubble()
     : SettingLevelBubble(
           ResourceBundle::GetSharedInstance().GetBitmapNamed(
               IDR_VOLUME_BUBBLE_UP_ICON),
           ResourceBundle::GetSharedInstance().GetBitmapNamed(
               IDR_VOLUME_BUBBLE_DOWN_ICON),
           ResourceBundle::GetSharedInstance().GetBitmapNamed(
               IDR_VOLUME_BUBBLE_MUTE_ICON)) {
 }
 
+// static
+VolumeBubble* VolumeBubble::instance() {
+  return Singleton<VolumeBubble>::get();
+}
+
 }  // namespace chromeos