Add ref count to service workers for extension API.

chrome/test/data/extensions/api_test/service_worker/api_worker_ref_count/page.js

Index: chrome/test/data/extensions/api_test/service_worker/api_worker_ref_count/page.js
diff --git a/chrome/test/data/extensions/api_test/service_worker/api_worker_ref_count/page.js b/chrome/test/data/extensions/api_test/service_worker/api_worker_ref_count/page.js
new file mode 100644
index 0000000000000000000000000000000000000000..0f26b96e0e51cd9a766ccb97f6582e3a1109c4fa
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/service_worker/api_worker_ref_count/page.js
@@ -0,0 +1,33 @@
+// Copyright 2016 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 worker = null;
+var FAILURE_MESSAGE = 'FAILURE';
+
+window.runServiceWorker = function() {
+  navigator.serviceWorker.register('sw.js').then(function() {
+    return navigator.serviceWorker.ready;
+  }).then(function(registration) {
+    worker = registration.active;
+    chrome.test.sendMessage('WORKER STARTED');
+  }).catch(function(err) {
+    chrome.test.sendMessage(FAILURE_MESSAGE);
+  });
+};
+
+window.testSendMessage = function() {
+  if (worker == null) {
+    chrome.test.sendMessage(FAILURE_MESSAGE);
+    return;
+  }
+  var channel = new MessageChannel();
+  channel.port1.onmessage = function(e) {
+    if (e.data == 'Worker reply: Hello world') {
+      chrome.test.sendMessage('SUCCESS');
+    } else {
+      chrome.test.sendMessage(FAILURE_MESSAGE);
+    }
+  };
+  worker.postMessage('sendMessageTest', [channel.port2]);
+};