Remove experimental code fro grouping notifications from the same source.

ui/message_center/views/message_center_controller.h

Index: ui/message_center/views/message_center_controller.h
diff --git a/ui/message_center/views/message_center_controller.h b/ui/message_center/views/message_center_controller.h
index 96b76f0d287b4db4b69968a319ed41008f0548a9..b770f467b4ae0aef119c224036a2be38f4a54e71 100644
--- a/ui/message_center/views/message_center_controller.h
+++ b/ui/message_center/views/message_center_controller.h
@@ -30,9 +30,6 @@ class MessageCenterController {
   virtual void ClickOnNotificationButton(const std::string& notification_id,
                                          int button_index) = 0;
   virtual void ExpandNotification(const std::string& notification_id) = 0;
-  virtual void GroupBodyClicked(const std::string& last_notification_id) = 0;
-  virtual void ExpandGroup(const NotifierId& notifier_id) = 0;
-  virtual void RemoveGroup(const NotifierId& notifier_id) = 0;
 };
 
 }  // namespace message_center