Reverting 12485 and 12480 just for the sake of mocking,

lib/isolate/base.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 IsolateSpawnException implements Exception {
   const IsolateSpawnException(String this._s);
   String toString() => "IsolateSpawnException: '$_s'";
   final String _s;
 }
 
@@ skipping 46 matching lines @@
    * the receiving isolate. If specified, the [replyTo] port will be provided to
    * the receiver to facilitate exchanging sequences of messages.
    *
    * The content of [message] can be: primitive values (null, num, bool, double,
    * String), instances of [SendPort], and lists and maps whose elements are any
    * of these. List and maps are also allowed to be cyclic.
    *
    * In the special circumstances when two isolates share the same code and are
    * running in the same process (e.g. isolates created via [spawnFunction]), it
    * is also possible to send object instances (which would be copied in the
-   * process). This is currently only supported by the dartvm.
+   * process). This is currently only supported by the dartvm.  For now, the
+   * frog compiler only supports the restricted messages described above.
    *
    * Deprecation note: it is no longer valid to transmit a [ReceivePort] in a
    * message. Previously they were translated to the corresponding send port
    * before being transmitted.
    */
   void send(var message, [SendPort replyTo]);
 
   /**
    * Sends a message to this send port and returns a [Future] of the reply.
    * Basically, this internally creates a new receive port, sends a
@@ skipping 60 matching lines @@
 // TODO(kasperl): Make this hashable and document it.
 abstract class SendPortSync {
 
   callSync(var message);
 
 }
 
 class _ReceivePortFactory {
   external factory ReceivePort();
 }