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

chrome/browser/chromeos/brightness_bubble.h

Index: chrome/browser/chromeos/brightness_bubble.h
diff --git a/chrome/browser/chromeos/brightness_bubble.h b/chrome/browser/chromeos/brightness_bubble.h
index 89553fcf4a364d23054dda4a262824cd1a3a11b4..7b5ed8c5cf9a47d2b7d197fba0829fb24dda93e3 100644
--- a/chrome/browser/chromeos/brightness_bubble.h
+++ b/chrome/browser/chromeos/brightness_bubble.h
@@ -16,7 +16,7 @@ namespace chromeos {
 // Singleton class controlling brightness bubble.
 class BrightnessBubble : public SettingLevelBubble {
  public:
-  static BrightnessBubble* instance();
+  static BrightnessBubble* GetInstance();
 
  private:
   friend struct DefaultSingletonTraits<BrightnessBubble>;