The Service Worker notificationclick event should carry a notification.

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
new file mode 100644
index 0000000000000000000000000000000000000000..d71f84ea01507e048340bac3c5356c9836e43280
--- /dev/null
+++ b/LayoutTests/http/tests/notifications/resources/click-close-service-worker.js
@@ -0,0 +1,13 @@
+// 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);
+});