anchor.diff:  
   class ExampleService extends Service {
     String serviceId = "example";
  +
     ExampleService(Services services, _IsolateHandler handler)
         : super(services, handler);
   }
  
positive.code:         _sendPort = arg;
          _readyController..add(null)..close();
        } else {
          // TODO(ericarnold): Temporary (encode ping command once implemented)
          _pong(arg);
  
          // implemented ...
          String data = arg["data"];
          Map dataMap = null;
          if (data != null) {
            dataMap = JSON.decode(data);
          }
          ActionEvent event = new ActionEvent(
              arg["serviceId"], arg["actionId"], arg["callId"], dataMap);
          messageController..add(event);
        }
      });
  
  
negative.code:     return _isolateHandler.onceIsolateReady.then((_){
        _isolateHandler.sendAction(serviceId, actionId, callId);
        return _isolateHandler.onIsolateResponse(callId).first;
      }).then((ServiceActionEvent event){
        print("pong");
        return new Future.value("poong");
      });
  