Allow partial update for notification update API

chrome/browser/notifications/notification_ui_manager_impl.cc

 // 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.
 
 #include "chrome/browser/notifications/notification_ui_manager_impl.h"
 
 #include "base/logging.h"
 #include "base/prefs/pref_service.h"
 #include "base/memory/linked_ptr.h"
 #include "base/stl_util.h"
@@ skipping 56 matching lines @@
     return;
   }
 
   VLOG(1) << "Added notification. URL: "
           << notification.content_url().spec();
   show_queue_.push_back(linked_ptr<QueuedNotification>(
       new QueuedNotification(notification, profile)));
   CheckAndShowNotifications();
 }
 
-bool NotificationUIManagerImpl::DoesIdExist(const std::string& id) {
+bool NotificationUIManagerImpl::DoesIdExist(
+    const std::string& id, Notification* matched_notification) {
   for (NotificationDeque::iterator iter = show_queue_.begin();
        iter != show_queue_.end(); ++iter) {
-    if ((*iter)->notification().notification_id() == id)
+    if ((*iter)->notification().notification_id() == id) {
+      if (matched_notification)
+        *matched_notification = (*iter)->notification();
       return true;
+    }
   }
   return false;
 }
 
 bool NotificationUIManagerImpl::CancelById(const std::string& id) {
   // See if this ID hasn't been shown yet.
   for (NotificationDeque::iterator iter = show_queue_.begin();
        iter != show_queue_.end(); ++iter) {
     if ((*iter)->notification().notification_id() == id) {
       show_queue_.erase(iter);
@@ skipping 141 matching lines @@
       CancelAllBySourceOrigin(extension->url());
     }
   } else if (type == chrome::NOTIFICATION_PROFILE_DESTROYED) {
     // We only want to remove the incognito notifications.
     if (content::Source<Profile>(source)->IsOffTheRecord())
       CancelAllByProfile(content::Source<Profile>(source).ptr());
   } else {
     NOTREACHED();
   }
 }