Upstream service worker message event tests to WPT

third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/ServiceWorkerGlobalScope/resources/extendable-message-event-pong-worker.js

+importScripts('./extendable-message-event-utils.js');
+
 self.addEventListener('message', function(event) {
     switch (event.data.type) {
       case 'ping':
-        var results = [
-            'Ping message: ' + event,
-            '  event.origin: ' + event.origin,
-            '  event.lastEventId: ' + event.lastEventId,
-            '  event.source: ' + event.source,
-            '  event.source.scriptURL: ' + event.source.scriptURL,
-            '  event.source.state: ' + event.source.state,
-            '  event.ports: ' + event.ports,
-        ];
+        var results = {
+            pingOrPong: 'ping',
+            event: ExtendableMessageEventUtils.serialize(event)
+        };
         var client_id = event.data.client_id;
         event.waitUntil(clients.get(client_id)
             .then(function(client) {
                 client.postMessage({type: 'record', results: results});
                 event.source.postMessage({type: 'pong', client_id: client_id});
               }));
         break;
     }
   });