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

chrome/browser/chromeos/volume_bubble.h

Index: chrome/browser/chromeos/volume_bubble.h
diff --git a/chrome/browser/chromeos/volume_bubble.h b/chrome/browser/chromeos/volume_bubble.h
index efbdc5f961b137d34bf7b0ce7739f417995ee035..17f72fc1a19190531045f546058336a2b61af3e0 100644
--- a/chrome/browser/chromeos/volume_bubble.h
+++ b/chrome/browser/chromeos/volume_bubble.h
@@ -16,7 +16,7 @@ namespace chromeos {
 // Singleton class controlling volume bubble.
 class VolumeBubble : public SettingLevelBubble {
  public:
-  static VolumeBubble* instance();
+  static VolumeBubble* GetInstance();
 
  private:
   friend struct DefaultSingletonTraits<VolumeBubble>;