Allow partial update for notification update API

chrome/renderer/resources/extensions/notifications_custom_bindings.js

 // Copyright 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.
 
 // Custom bindings for the notifications API.
 var binding = require('binding').Binding.create('notifications');
 
 var sendRequest = require('sendRequest').sendRequest;
 var imageUtil = require('imageUtil');
 var lastError = require('lastError');
 
 function image_data_setter(context, key) {
   var f = function(val) {
     this[key] = val;
   };
   return $Function.bind(f, context);
 }
 
 function replaceNotificationOptionURLs(notification_details, callback) {
   // A URL Spec is an object with the following keys:
   //  path: The resource to be downloaded.
   //  width: (optional) The maximum width of the image to be downloaded.
   //  height: (optional) The maximum height of the image to be downloaded.
   //  callback: A function to be called when the URL is complete. It
   //    should accept an ImageData object and set the appropriate
   //    field in the output of create.
 
+  // |iconUrl| might be optional for notification updates.
+  if (!notification_details.iconUrl) {
+    callback(true);

[dewittj, 2013/07/24 23:09:53]

What if all they want to update is the image url, or the button icon urls?  This
logic won't work here.

[jianli, 2013/07/25 01:02:41]

Done.

+    return;
+  }
+
   // TODO(dewittj): Try to remove hard-coding of image sizes.
-  // |iconUrl| is required.
   var url_specs = [{
     path: notification_details.iconUrl,
     width: 80,
     height: 80,
     callback: image_data_setter(notification_details, 'iconBitmap')
   }];
 
   // |imageUrl| is optional.
   if (notification_details.imageUrl) {
     $Array.push(url_specs, {
@@ skipping 69 matching lines @@
 
 var notificationsCustomHook = function(bindingsAPI, extensionId) {
   var apiFunctions = bindingsAPI.apiFunctions;
   apiFunctions.setHandleRequest('create', handleCreate);
   apiFunctions.setHandleRequest('update', handleUpdate);
 };
 
 binding.registerCustomHook(notificationsCustomHook);
 
 exports.binding = binding.generate();