Add a test to cover service worker update codepath when extension is updated

chrome/test/data/extensions/api_test/service_worker/update/v2/background.js

+// Copyright 2015 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.
+
+var controllerChangePromise = new Promise(function(resolve, reject) {
+  navigator.serviceWorker.oncontrollerchange = function(e) {
+    navigator.serviceWorker.ready.then(function(registration) {
+      resolve(registration.active);
+    }).catch(function(err) {
+      reject('oncontrollerchange failure');
+    });
+  };
+});
+
+var registerServiceWorkerPromise = new Promise(function(resolve, reject) {
+  navigator.serviceWorker.register('sw.js').then(function() {

[falken, 2015/12/09 02:31:41]

Since you're testing update, I would just get rid of this register() call. I was
worried the test is "cheating" by calling register, which could trigger an
update, whereas we want to test that the update occurs automatically.

It turns out no cheating is going on, since the script url has not changed,
which turns register() into a no-op. For simplicity, you can just remove it
though.

For that matter, you could get rid of this whole registerServiceWorkerPromise,
and only use controllerChangePromise.

[Devlin, 2015/12/09 17:09:07]

+1. If calling register with the same script url is ever not a no-op, this would
invalidate the test (silently).

[lazyboy, 2015/12/09 18:55:57]

Done.

[lazyboy, 2015/12/09 18:55:57]

Done.

+    return navigator.serviceWorker.ready;
+  }).then(function(registration) {
+    resolve(registration.active);
+  }).catch(function(err) {
+    reject(err);
+  });
+});
+
+Promise.all([controllerChangePromise, registerServiceWorkerPromise])
+    .then(function(results) {
+  var serviceWorker = results[0];
+  var channel = new MessageChannel();
+  channel.port1.onmessage = function(e) {
+    console.log('Message received from SW: ' + e.data);

[Devlin, 2015/12/09 17:09:07]

chrome.test.log (or remove)

[lazyboy, 2015/12/09 18:55:58]

Done.

+    chrome.test.sendMessage(e.data);
+  };
+  serviceWorker.postMessage('ping', [channel.port2]);
+}).catch(function(err) {
+  console.log(err);
+  chrome.test.sendMessage('FAILURE_V2');
+});