Build fix for clang bot.

TBR=alicet
Review URL: http://codereview.chromium.org/8418042

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@107833 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/chromeos/setting_level_bubble.h

@@ -61,7 +61,7 @@ class SettingLevelBubble : public views::Widget::Observer {
   FRIEND_TEST_ALL_PREFIXES(VolumeBubbleTest, GetInstanceAndShow);
 
   // views::Widget::Observer overrides:
-  void OnWidgetClosing(views::Widget* widget) OVERRIDE;
+  virtual void OnWidgetClosing(views::Widget* widget) OVERRIDE;
 
   // Creates the bubble content view.
   // Caller should call Init() on the returned SettingLevelBubbleView.