extensions: Migrate other uses of webkitNotifications to Web Notifications API.

chrome/common/extensions/docs/templates/articles/cloudMessagingV1.html

 <meta name="doc-family" content="apps">
 <h1>Google Cloud Messaging for Chrome V1</h1>
 
 <p class="note">
 Google Cloud Messaging for Chrome V1 will be legacy soon.
 Use the new <a href="cloudMessaging">Google Cloud Messaging API</a>.
 </p>
 
 <p>
 Google Cloud Messaging for Chrome (GCM) is a service
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 for the contents of previous messages and
 to get data if the payload is not present.
 </p>
 
 <p>Here's a simple example that shows a push message
 as a text notification when it arrives:
 </p>
 
 <pre>
 function showPushMessage(message) {
-  var notification = window.webkitNotifications.createNotification(
-    '', 'New notification', message.payload + " [" + message.subchannelId + "]");
-  notification.show();
+  new Notification('New notification', {
+    body: message.payload + " [" + message.subchannelId + "]"
+  });
 }
 </pre>
 
 <p>
 You need to add the "notifications" permission
 to <code>manifest.json</code>
 to use text notifications
 (see <a href="desktop_notifications">Desktop Notifications</a>):
 </p>
 
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 you need to remove the key because the Store does not currently allow manifests
 with keys.
 </p>
 
 <h2 id="feedback">Feedback</h2>
 
 <p>You can provide feedback about Google Cloud Messaging
 and the pushMessaging API through the Google Group
 <a target="_blank" href="https://groups.google.com/forum/#!forum/gcm-for-chrome-feedback">GCM for Chrome feedback</a>.
 Use this group to ask for help, file bug reports, and request features.</p>