Allow partial update for notification update API

chrome/browser/notifications/balloon_collection.h

 // Copyright (c) 2011 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.
 
 // Handles the visible notification (or balloons).
 
 #ifndef CHROME_BROWSER_NOTIFICATIONS_BALLOON_COLLECTION_H_
 #define CHROME_BROWSER_NOTIFICATIONS_BALLOON_COLLECTION_H_
 
 #include <deque>
@@ skipping 37 matching lines @@
 
   BalloonCollection();
 
   virtual ~BalloonCollection();
 
   // Adds a new balloon for the specified notification.
   virtual void Add(const Notification& notification,
                    Profile* profile) = 0;
 
   // Returns true if any balloon has this notification id.
-  virtual bool DoesIdExist(const std::string& id) = 0;
+  virtual const Notification* FindById(const std::string& id) const = 0;
 
   // Removes any balloons that have this notification id. Returns
   // true if anything was removed.
   virtual bool RemoveById(const std::string& id) = 0;
 
   // Removes any balloons that have this source origin. Returns
   // true if anything was removed.
   virtual bool RemoveBySourceOrigin(const GURL& source_origin) = 0;
 
   // Removes any balloons matching |profile. Returns true if any were removed.
@@ skipping 35 matching lines @@
  protected:
   // Non-owned pointer to an object listening for space changes.
   BalloonSpaceChangeListener* space_change_listener_;
 
   // For use only with testing. This callback is invoked when a balloon
   // is added or removed from the collection.
   base::Closure on_collection_changed_callback_;
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_BALLOON_COLLECTION_H_