Replace more ObserverList with base::ObserverList.

ui/message_center/message_center_impl.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_MESSAGE_CENTER_IMPL_H_
 #define UI_MESSAGE_CENTER_MESSAGE_CENTER_IMPL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 197 matching lines @@
 
     NotificationList::Notifications visible_notifications;
     size_t unread_count;
   };
 
   void RemoveNotifications(bool by_user, const NotificationBlockers& blockers);
   void RemoveNotificationsForNotifierId(const NotifierId& notifier_id);
 
   scoped_ptr<NotificationList> notification_list_;
   NotificationCache notification_cache_;
-  ObserverList<MessageCenterObserver> observer_list_;
+  base::ObserverList<MessageCenterObserver> observer_list_;
   scoped_ptr<internal::PopupTimersController> popup_timers_controller_;
   scoped_ptr<base::OneShotTimer<MessageCenterImpl> > quiet_mode_timer_;
   NotifierSettingsProvider* settings_provider_;
   std::vector<NotificationBlocker*> blockers_;
 
   // Queue for the notifications to delay the addition/updates when the message
   // center is visible.
   scoped_ptr<internal::ChangeQueue> notification_queue_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageCenterImpl);
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_MESSAGE_CENTER_H_