anchor.diff:  import 'services_impl.dart' as services_impl;
   
   IsolateHandler createIsolateHandler() {
  -  return new _IsolateHandlerSingleThreadImpl();  
  +  return new _IsolateHandlerSingleThreadImpl();
   }
   
   class StreamWorkerPort implements WorkerPort {
  
positive.code:       }
      }
    }
    
    @override
    Future<String> ping() {
      Completer<String> completer = new Completer();
      
      int callId = _topCallId;
      _serviceCallCompleters["ping_$callId"] = completer;
      onceIsolateReady.then((_) {
        _port.sendToHost(callId);
      });
      _topCallId += 1;
      
      return completer.future;
    }
  
  
negative.code:   }
  
    String _getNewCallId() => "host_${_topCallId++}";
  
    @override
    Future<ServiceActionEvent> sendAction(ServiceActionEvent event) {
      Completer<ServiceActionEvent> completer =
  