Expose ServiceWorkerRegistration.showNotification() in Service Workers.

LayoutTests/http/tests/notifications/resources/test-helpers.js

Index: LayoutTests/http/tests/notifications/resources/test-helpers.js
diff --git a/LayoutTests/http/tests/notifications/resources/test-helpers.js b/LayoutTests/http/tests/notifications/resources/test-helpers.js
index 7706199464431c09c5f6227d61b80ffd1f5d7637..b9c06b2b7eb514256471068e98f21763b4779ac8 100644
--- a/LayoutTests/http/tests/notifications/resources/test-helpers.js
+++ b/LayoutTests/http/tests/notifications/resources/test-helpers.js
@@ -36,4 +36,33 @@ function sharedWorkerTest(script)
 function isDedicatedOrSharedWorker()
 {
     return false;
-}
+}
+
+// Unregisters, then registers the Service Worker in |script| using |scope|, waits
+// for it to activate and then inserts a message port. Returns a Promise which will
+// be resolved with an object having the worker's registration and port. The
+// Service Worker will be automatically unregistered once the test has completed.
+function getActiveServiceWorkerWithMessagePort(test, script, scope)
+{
+    var registration = null;
+    return service_worker_unregister_and_register(test, script, scope).then(function(swRegistration) {
+        registration = swRegistration;
+        add_completion_callback(function() {
+            registration.unregister();
+        });
+
+        return wait_for_state(test, registration.installing, 'activated');
+    }).then(function() {
+        assert_not_equals(registration.active, null, 'The Service Worker needs to be activated.');
+        return new Promise(function(resolve) {
+            var messageChannel = new MessageChannel();
+            messageChannel.port1.addEventListener('message', function(event) {
+                if (event.data == 'ready')
+                    resolve({ registration: registration, port: messageChannel.port1 });
+            });
+
+            registration.active.postMessage(messageChannel.port2, [messageChannel.port2]);
+            messageChannel.port1.start();
+        });
+    });
+}