anchor.diff:          _globalState.topEventLoop.run();
           break;
         case 'spawn-worker':
  -        var replyPort = msg['replyPort'];
  -        spawn(msg['functionName'], msg['uri'],
  -              msg['args'], msg['msg'],
  -              false, msg['isSpawnUri'], msg['startPaused']).then((msg) {
  -          replyPort.send(msg);
  -        }, onError: (String errorMessage) {
  -          replyPort.send([_SPAWN_FAILED_SIGNAL, errorMessage]);
  -        });
  +        if (enableSpawnWorker != null) handleSpawnWorkerRequest(msg);
           break;
         case 'message':
           SendPort port = msg['port'];
  
positive.code: /// when 'dart:isolate' has been imported.
  class IsolateNatives {
  
    static String thisScript = computeThisScript();
  
    /// Associates an ID with a native worker object.
  
negative.code: 
    static Future<List> spawnUri(Uri uri, List<String> args, var message,
                                 bool startPaused) {
      IsolateNatives.enableSpawnWorker = true;
      bool isLight = false;
      bool isSpawnUri = true;
      return spawn(null, uri.toString(), args, message,
  