Added Dartium support for JS to Dart PortSync calls

lib/dom/templates/html/dartium/impl_Window.darttemplate

 // 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.
 
 class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
   void requestLayoutFrame(TimeoutHandler callback) {
     _addMeasurementFrameCallback(callback);
   }
 
   int requestAnimationFrame(RequestAnimationFrameCallback callback) =>
       webkitRequestAnimationFrame(callback);
 
   void cancelAnimationFrame(int id) => webkitCancelAnimationFrame(id);
 
   IDBFactory get indexedDB() => webkitIndexedDB;
 
-  // TODO(kasperl): Document this.
+  // TODO(kasperl): Document these.
   lookupPort(String name) {
     var port = JSON.parse(localStorage['dart-port:$name']);
     return _deserialize(port);
   }
 
+  registerPort(String name, var port) {
+    var serialized = _serialize(port);
+    localStorage['dart-port:$name'] = JSON.stringify(serialized);
+  }
+
 $!MEMBERS
 }