Allow partial update for notification update API

chrome/browser/notifications/message_center_notification_manager.h

 // Copyright (c) 2012 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 CHROME_BROWSER_NOTIFICATIONS_MESSAGE_CENTER_NOTIFICATION_MANAGER_H_
 #define CHROME_BROWSER_NOTIFICATIONS_MESSAGE_CENTER_NOTIFICATION_MANAGER_H_
 
 #include <map>
 #include <string>
 
@@ skipping 20 matching lines @@
     : public NotificationUIManagerImpl,
       public message_center::MessageCenter::Delegate,
       public message_center::MessageCenterObserver {
  public:
   explicit MessageCenterNotificationManager(
       message_center::MessageCenter* message_center,
       PrefService* local_state);
   virtual ~MessageCenterNotificationManager();
 
   // NotificationUIManager
-  virtual bool DoesIdExist(const std::string& notification_id) OVERRIDE;
+  virtual const Notification* FindById(
+      const std::string& notification_id) const OVERRIDE;
   virtual bool CancelById(const std::string& notification_id) OVERRIDE;
   virtual std::set<std::string> GetAllIdsByProfileAndSourceOrigin(
       Profile* profile,
       const GURL& source) OVERRIDE;
   virtual bool CancelAllBySourceOrigin(const GURL& source_origin) OVERRIDE;
   virtual bool CancelAllByProfile(Profile* profile) OVERRIDE;
   virtual void CancelAll() OVERRIDE;
 
   // NotificationUIManagerImpl
   virtual bool ShowNotification(const Notification& notification,
@@ skipping 158 matching lines @@
   // Provides weak pointers for the purpose of the first run timer.
   base::WeakPtrFactory<MessageCenterNotificationManager> weak_factory_;
 #endif
 
   scoped_ptr<MessageCenterSettingsController> settings_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageCenterNotificationManager);
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_MESSAGE_CENTER_NOTIFICATION_MANAGER_H_