implement on notification click

serviceworker.js

@@ -20,3 +20,27 @@ this.addEventListener('push', function(event) {
           tag: 'my-tag'
         }));
 });
+
+this.onnotificationclick = function(event) {
+    // Android doesn't close the notification when you click on it
+    // See: http://crbug.com/463146
+    event.notification.close();
+
+    // This looks to see if the current is already open and
+    // focuses if it is
+    event.waitUntil(clients.matchAll({
+        type: "window"
+    }).then(function(clientList) {
+        for (var i = 0; i < clientList.length; i++) {
+            var client = clientList[i];
+            if ('focus' in client) {
+                return client.focus();
+            }
+        }
+        /*
+        if (clients.openWindow) {
+            return clients.openWindow('/glowing-bear/');
+        }
+        */
+    }));
+};