Expose ServiceWorkerRegistration.showNotification() in Service Workers.

LayoutTests/http/tests/notifications/resources/click-close-service-worker.js

Index: LayoutTests/http/tests/notifications/resources/click-close-service-worker.js
diff --git a/LayoutTests/http/tests/notifications/resources/click-close-service-worker.js b/LayoutTests/http/tests/notifications/resources/click-close-service-worker.js
deleted file mode 100644
index d71f84ea01507e048340bac3c5356c9836e43280..0000000000000000000000000000000000000000
--- a/LayoutTests/http/tests/notifications/resources/click-close-service-worker.js
+++ /dev/null
@@ -1,13 +0,0 @@
-// Sends a message when the notificationclick event gets received, and closes the
-// notification which was shown from that event.
-var messagePort = null;
-
-addEventListener('message', function(event) {
-    messagePort = event.data;
-    messagePort.postMessage('ready');
-});
-
-addEventListener('notificationclick', function(event) {
-    event.notification.close();
-    messagePort.postMessage('Clicked on Notification: ' + event.notification.title);
-});