anchor.diff:    static Future<List> spawnFunction(void topLevelFunction(message),
                                       var message,
                                       bool startPaused) {
  +    IsolateNatives.enableSpawnWorker = true;
       final name = _getJSFunctionName(topLevelFunction);
       if (name == null) {
         throw new UnsupportedError(
  
positive.code: 
    static Future<List> spawnUri(Uri uri, List<String> args, var message,
                                 bool startPaused) {
      bool isLight = false;
      bool isSpawnUri = true;
      return spawn(null, uri.toString(), args, message,
  
negative.code:         _globalState.topEventLoop.run();
          break;
        case 'spawn-worker':
          if (enableSpawnWorker != null) handleSpawnWorkerRequest(msg);
          break;
        case 'message':
          SendPort port = msg['port'];
  