anchor.diff:    Future onceIsolateReady;
   
     _IsolateHandler() {
  +    onIsolateMessage = _messageController.stream;
  +    onceIsolateReady = _readyController.stream.first;
  +    _startIsolate();
  +
       // TODO(ericarnold): Implement
     }
   
  
positive.code:         _sendPort = arg;
          _readyController..add(null)..close();
        } else {
          pong(arg);
        }
      });
  
  
negative.code:     return completer.future;
    }
  
    Future _pong(int id) {
      Completer completer = _serviceCallCompleters[id];
      _serviceCallCompleters.remove(id);
      completer.complete("pong");
  