Extension SW: Add tests that serve web_accessible_resources from a SW.

chrome/test/data/extensions/api_test/service_worker/web_accessible_resources/iframe_src/background.js

Index: chrome/test/data/extensions/api_test/service_worker/web_accessible_resources/iframe_src/background.js
diff --git a/chrome/test/data/extensions/api_test/service_worker/web_accessible_resources/iframe_src/background.js b/chrome/test/data/extensions/api_test/service_worker/web_accessible_resources/iframe_src/background.js
new file mode 100644
index 0000000000000000000000000000000000000000..a3555049d081da6f4881ef739ec2d4eb20d65fe0
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/service_worker/web_accessible_resources/iframe_src/background.js
@@ -0,0 +1,15 @@
+// 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.
+
+window.registerServiceWorker = function() {
+  navigator.serviceWorker.register('sw.js').then(function(registration) {
+    return navigator.serviceWorker.ready;
+  }).then(function(registration) {
+    chrome.test.sendMessage('SW_READY');
+  }).catch(function(err) {
+    chrome.test.log('SW registration failure: ' + err);
+    chrome.test.sendMessage('SW_FAILED');
+  });
+  return "true";
+};