Tests for WaitUntilObserver and focus/openining windows.

LayoutTests/http/tests/serviceworker/resources/notificationclick-can-focus.js

+var client = null;
+
+function initializeClient() {
+    return self.clients.getAll().then(function(clients) {
+        client = clients[0];
+    });
+}
+
+function testWithClick() {
+    var notification = new Notification('My Notification');
+    notification.addEventListener('show', function() {
+        client.postMessage('click');
+    });
+
+    notification.addEventListener('click', function() {
+        client.focus().catch(function() {
+            client.postMessage('focus() outside of a notificationclick failed');
+            client.postMessage('quit');
+        });
+    });
+
+    notification.addEventListener('error', function() {
+        client.postMessage('quit');
+    });
+
+    client.postMessage('quit');
+}
+
+function testWithNoClick() {
+    client.focus().catch(function() {
+        client.postMessage('focus() outside of a notificationclick failed');
+        testWithClick();
+    });
+}
+
+self.onmessage = function(e) {
+    switch(e.data) {
+        case "start":
+            initializeClient().then(testWithNoClick);
+            break;
+    }
+}