Make the new JS interop test pass on Dartium.

client/dart.js

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Bootstrap support for Dart scripts on the page as this script.
 if (navigator.webkitStartDart) {
   if (!navigator.webkitStartDart()) {
     document.body.innerHTML = 'This build has expired.  Please download a new Dartium at http://www.dartlang.org/dartium/index.html';
   }
 } else {
@@ skipping 47 matching lines @@
   return new SendPortSync(this);
 };
 
 ReceivePortSync.prototype.close = function() {
   delete ReceivePortSync.map[this.id];
 };
 
 // TODO(kasperl): Hide these serialization methods so they
 // do not clutter up the global scope.
 function _serialize(message) {
-  if (message == null ||
-      typeof(message) == 'string' ||
-      typeof(message) == 'number' ||
-      typeof(message) == 'boolean') {
+  if (message == null) {
+    return null;  // Convert undefined to null.
+  } else if (typeof(message) == 'string' ||
+             typeof(message) == 'number' ||
+             typeof(message) == 'boolean') {
     return message;
   } else if (message instanceof SendPortSync) {
     return [ 'sendport', message.receivePort.id ];
   } else {
     var id = 0;
     var keys = Object.getOwnPropertyNames(message);
     var values = new Array(keys.length);
     for (var i = 0; i < keys.length; i++) {
       values[i] = message[keys[i]];
     }
@@ skipping 28 matching lines @@
     var value = _deserializeHelper(values[i]);
     result[key] = value;
   }
   return result;
 }
 
 function registerPort(name, port) {
   var stringified = JSON.stringify(_serialize(port));
   window.localStorage['dart-port:' + name] = stringified;
 }
+
+if (navigator.webkitStartDart) {
+  window.addEventListener('js-sync-message', function(event) {
+    var data = JSON.parse(event.data);
+    var deserialized = _deserialize(data.message);
+    var result = ReceivePortSync.map[data.id].callback(deserialized);
+    var string = JSON.stringify(_serialize(result));
+    var event = document.createEvent('TextEvent');
+    event.initTextEvent('js-result', false, false, window, string);
+    window.dispatchEvent(event);
+  }, false);
+}