Add layout tests for ServiceWorker's notificationclose event.

third_party/WebKit/LayoutTests/http/tests/notifications/resources/instrumentation-service-worker.js

 importScripts('/resources/testharness-helpers.js');
 
 // For copying Notification.data. Currently a deep copy algorithm is used. Note
 // that the robustness of this function (and also |assert_object_equals| in
 // testharness.js) affects the types of possible testing can be done.
 // TODO(peter): change this to a structured clone algorithm.
 function cloneObject(src) {
     if (typeof src != 'object' || src === null)
         return src;
     var dst = Array.isArray(src) ? [] : {};
@@ skipping 84 matching lines @@
 
     // Notifications containing "ACTION:OPENWINDOW" in their message will attempt
     // to open a new window for an example URL.
     if (event.notification.body.indexOf('ACTION:OPENWINDOW') != -1)
         event.waitUntil(clients.openWindow('https://example.com/'));
 
     messagePort.postMessage({ command: 'click',
                               notification: notificationCopy,
                               action: event.action });
 });
+
+addEventListener('notificationclose', function(event) {
+    var notificationCopy = cloneNotification(event.notification);
+    messagePort.postMessage({ command: 'close',
+                              notification: notificationCopy });
+});