Mark create/update/clear callbacks of notification API as optional

chrome/common/extensions/api/notifications.idl

 // 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.
 
 // Use the <code>chrome.notifications</code> API to create rich notifications
 // using templates and show these notifications to users in the system tray.
 namespace notifications {
   [noinline_doc] enum TemplateType {
     // icon, title, message, expandedMessage, up to two buttons
     basic,
@@ skipping 115 matching lines @@
     // Creates and displays a notification.
     // |notificationId|: Identifier of the notification. If it is empty, this
     // method generates an id. If it matches an existing notification, this
     // method first clears that notification before proceeding with the create
     // operation.
     // |options|: Contents of the notification.
     // |callback|: Returns the notification id (either supplied or generated)
     // that represents the created notification.
     static void create(DOMString notificationId,
                        NotificationOptions options,
-                       CreateCallback callback);
+                       optional CreateCallback callback);
 
     // Updates an existing notification.
     // |notificationId|: The id of the notification to be updated. This is
     // returned by $(ref:notifications.create) method.
     // |options|: Contents of the notification to update to.
     // |callback|: Called to indicate whether a matching notification existed.
     static void update(DOMString notificationId,
                        NotificationOptions options,
-                       UpdateCallback callback);
+                       optional UpdateCallback callback);
 
     // Clears the specified notification.
     // |notificationId|: The id of the notification to be cleared. This is
     // returned by $(ref:notifications.create) method.
     // |callback|: Called to indicate whether a matching notification existed.
-    static void clear(DOMString notificationId, ClearCallback callback);
+    static void clear(DOMString notificationId,
+                      optional ClearCallback callback);
 
     // Retrieves all the notifications.
     // |callback|: Returns the set of notification_ids currently in the system.
     static void getAll(GetAllCallback callback);
 
     // Retrieves whether the user has enabled notifications from this app
     // or extension.
     // |callback|: Returns the current permission level.
     static void getPermissionLevel(PermissionLevelCallback callback);
   };
 
   interface Events {
     // The notification closed, either by the system or by user action.
     static void onClosed(DOMString notificationId, boolean byUser);
 
     // The user clicked in a non-button area of the notification.
     static void onClicked(DOMString notificationId);
 
     // The user pressed a button in the notification.
     static void onButtonClicked(DOMString notificationId, long buttonIndex);
 
     // The user changes the permission level.
     static void onPermissionLevelChanged(PermissionLevel level);
 
     // The user clicked on a link for the app's notification settings.
     static void onShowSettings();
   };
 
 };