Extension SW - add basic push messaging tests.

chrome/test/data/extensions/api_test/service_worker/push_messaging/sw.js

Index: chrome/test/data/extensions/api_test/service_worker/push_messaging/sw.js
diff --git a/chrome/test/data/extensions/api_test/service_worker/push_messaging/sw.js b/chrome/test/data/extensions/api_test/service_worker/push_messaging/sw.js
new file mode 100644
index 0000000000000000000000000000000000000000..8623382cfbf3a85de44a179e313711ef964ef9ec
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/service_worker/push_messaging/sw.js
@@ -0,0 +1,24 @@
+// 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 port;
+var pushData;
+
+function maybeFinish() {
+  if (port && pushData) {
+    port.postMessage(pushData);
+  }
+}
+
+this.onpush = function(e) {
+  pushData = e.data.text();
+  maybeFinish();
+};
+
+this.onmessage = function(e) {
+  if (e.data == 'waitForPushMessaging') {
+    port = e.ports[0];
+    maybeFinish();
+  }
+};