Support persistent notifications in the PlatformNotificationServiceImpl.

chrome/test/data/notifications/platform_notification_service.js

Index: chrome/test/data/notifications/platform_notification_service.js
diff --git a/chrome/test/data/notifications/platform_notification_service.js b/chrome/test/data/notifications/platform_notification_service.js
new file mode 100644
index 0000000000000000000000000000000000000000..430abd77fc9b58fb1b3efc0cd34017bf36621ae4
--- /dev/null
+++ b/chrome/test/data/notifications/platform_notification_service.js
@@ -0,0 +1,17 @@
+// Service Worker to be used with the platform_notification_service.html page.
+var messagePort = null;
+
+addEventListener('message', function (event) {
+  messagePort = event.data;
+  messagePort.postMessage('ready');
+});
+
+// The notificationclick event will be invoked when a persistent notification
+// has been clicked on. When this happens, the title determines whether this
+// Service Worker has to act upon this.
+addEventListener('notificationclick', function (event) {
+  if (event.notification.title == 'action_close')
+    event.notification.close();
+
+  messagePort.postMessage(event.notification.title);
+});