anchor.diff:  
     // Fired when isolate responds to message
     Stream<ServiceActionEvent> onIsolateResponse(String callId) {
  -    onIsolateMessage = _messageController.stream;
  -    onceIsolateReady = _readyController.stream.first;
       // TODO(ericarnold): Implement
     }
   
  
positive.code:     return completer.future;
    }
  
    Future pong(int id) {
      Completer completer = _serviceCallCompleters[id];
      _serviceCallCompleters.remove(id);
      completer.complete("pong");
  
negative.code:   Future onceIsolateReady;
  
    _IsolateHandler() {
      onIsolateMessage = _messageController.stream;
      onceIsolateReady = _readyController.stream.first;
      _startIsolate();
  
      // TODO(ericarnold): Implement
    }
  
  