Remove experimental code fro grouping notifications from the same source.

ui/message_center/views/message_popup_collection.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_MESSAGE_CENTER_VIEWS_MESSAGE_POPUP_COLLECTION_H_
 #define UI_MESSAGE_CENTER_VIEWS_MESSAGE_POPUP_COLLECTION_H_
 
 #include <list>
 #include <map>
 
@@ skipping 64 matching lines @@
   virtual void ClickOnNotification(const std::string& notification_id) OVERRIDE;
   virtual void RemoveNotification(const std::string& notification_id,
                                   bool by_user) OVERRIDE;
   virtual scoped_ptr<ui::MenuModel> CreateMenuModel(
       const NotifierId& notifier_id,
       const base::string16& display_source) OVERRIDE;
   virtual bool HasClickedListener(const std::string& notification_id) OVERRIDE;
   virtual void ClickOnNotificationButton(const std::string& notification_id,
                                          int button_index) OVERRIDE;
   virtual void ExpandNotification(const std::string& notification_id) OVERRIDE;
-  virtual void GroupBodyClicked(const std::string& last_notification_id)
-      OVERRIDE;
-  virtual void ExpandGroup(const NotifierId& notifier_id) OVERRIDE;
-  virtual void RemoveGroup(const NotifierId& notifier_id) OVERRIDE;
 
   void MarkAllPopupsShown();
 
   // Since these events are really coming from individual toast widgets,
   // it helps to be able to keep track of the sender.
   void OnMouseEntered(ToastContentsView* toast_entered);
   void OnMouseExited(ToastContentsView* toast_exited);
 
   // Invoked by toasts when they start/finish their animations.
   // While "defer counter" is greater then zero, the popup collection does
@@ skipping 123 matching lines @@
   // Gives out weak pointers to toast contents views which have an unrelated
   // lifetime.  Must remain the last member variable.
   base::WeakPtrFactory<MessagePopupCollection> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePopupCollection);
 };
 
 }  // namespace message_center
 
 #endif // UI_MESSAGE_CENTER_VIEWS_MESSAGE_POPUP_COLLECTION_H_