Add testing for subscription from service workers

chrome/test/data/push_messaging/service_worker.js

 // Copyright 2014 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.
 
+self.importScripts('push_constants.js');
+
+var pushSubscriptionOptions = {
+    userVisibleOnly: true
+};
+
 // The "onpush" event currently understands two values as message payload
 // data coming from the test. Any other input is passed through to the
 // document unchanged.
 //
 // "shownotification" - Display a Web Notification with event.waitUntil().
 // "shownotification-without-waituntil"
 //     - Display a Web Notification without using event.waitUntil().
 this.onpush = function(event) {
   if (event.data === null) {
     sendMessageToClients('push', '[NULL]');
@@ skipping 16 matching lines @@
     return;
   }
 
   event.waitUntil(result.then(function() {
     sendMessageToClients('push', data);
   }, function(ex) {
     sendMessageToClients('push', String(ex));
   }));
 };
 
+self.addEventListener('message', function handler (event) {
+  if (event.data.command == 'workerSubscribe') {
+    pushSubscriptionOptions.applicationServerKey = kApplicationServerKey.buffer;
+  } else if (event.data.command == 'workerSubscribePermissionFail') {

[Michael van Ouwerkerk, 2016/03/30 09:50:04]

This case appears to be unused?

[harkness, 2016/03/30 10:51:49]

Done.

+    pushSubscriptionOptions.applicationServerKey = kApplicationServerKey.buffer;
+    pushSubscriptionOptions.userVisibleOnly = false;
+  } else if (event.data.command == 'workerSubscribeNoKey') {
+    // Nothing to set up
+  } else {
+    sendMessageToClients('message', 'error - unknown message request');
+    return;
+  }
+
+  self.registration.pushManager.subscribe(pushSubscriptionOptions)
+      .then(function(subscription) {
+        sendMessageToClients('message', subscription.endpoint);
+      }, function(error) {
+        sendErrorToClients(error);
+      });
+});
+
+function sendErrorToClients(error) {
+  sendMessageToClients('error', error.name + ' - ' + error.message);
+}
+
 function sendMessageToClients(type, data) {
   var message = JSON.stringify({
     'type': type,
     'data': data
   });
   clients.matchAll().then(function(clients) {
     clients.forEach(function(client) {
       client.postMessage(message);
     });
   }, function(error) {
     console.log(error);
   });
 }