Add support for JS->Dart and Dart->dart via *PortSync.

lib/isolate/serialization.dart

 // 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 _MessageTraverserVisitedMap {
 
   operator[](var object) => null;
   void operator[]=(var object, var info) { }
 
   void reset() { }
@@ skipping 18 matching lines @@
       _visited.cleanup();
     }
     return result;
   }
 
   _dispatch(var x) {
     if (isPrimitive(x)) return visitPrimitive(x);
     if (x is List) return visitList(x);
     if (x is Map) return visitMap(x);
     if (x is SendPort) return visitSendPort(x);
+    if (x is SendPortSync) return visitSendPortSync(x);
 
     // TODO(floitsch): make this a real exception. (which one)?
     throw "Message serialization: Illegal value $x passed";
   }
 
   abstract visitPrimitive(x);
   abstract visitList(List x);
   abstract visitMap(Map x);
   abstract visitSendPort(SendPort x);
+  abstract visitSendPortSync(SendPortSync x);
 
   static bool isPrimitive(x) {
     return (x === null) || (x is String) || (x is num) || (x is bool);
   }
 }
 
 
 /** A visitor that recursively copies a message. */
 class _Copier extends _MessageTraverser {
 
@@ skipping 129 matching lines @@
       var key = _deserializeHelper(keys[i]);
       var value = _deserializeHelper(values[i]);
       result[key] = value;
     }
     return result;
   }
 
   abstract deserializeSendPort(List x);
 
 }