Fix the settings button and UMA metrics for the message center

ui/message_center/message_center_observer.h

Index: ui/message_center/message_center_observer.h
diff --git a/ui/message_center/message_center_observer.h b/ui/message_center/message_center_observer.h
index e6315ccb9299267ce08d0f8ca13dfd854b3b37c9..e738bcb910d563f5b879ee6c7a729e72afdcdeca 100644
--- a/ui/message_center/message_center_observer.h
+++ b/ui/message_center/message_center_observer.h
@@ -40,8 +40,9 @@ class MESSAGE_CENTER_EXPORT MessageCenterObserver {
   virtual void OnNotificationButtonClicked(const std::string& notification_id,
                                            int button_index) {}
 
-  // Called when notification settings button is clicked.
-  virtual void OnNotificationSettingsClicked() {}
+  // Called when notification settings button is clicked. The |handled| argument
+  // indicates whether the notification delegate already handled the operation.
+  virtual void OnNotificationSettingsClicked(bool handled) {}
 
   // Called when the notification associated with |notification_id| is actually
   // displayed.