anchor.diff:              }
           }
        };
  +     messageSubscription = poll.onMessage.listen(msgHandler);
        closeSubscription = poll.onClose.listen(closeHandler);
     }
   
  
positive.code:   var receiverFactory;
    String recvUrl;
    AjaxObjectFactory xhrFactory;
  
    XhrReceiver poll;
    StreamSubscription messageSubscription;
    StreamSubscription closeSubscription;
    
    bool pollIsClosing = false;
  
    Polling(this.ri, this.receiverFactory, this.recvUrl, this.xhrFactory) {
  
negative.code:       msg_counter += 1;
        ri._didMessage(e.data);
      };
      var messageSubscription, closeSubscription;
  
      var closeHandler = (e) {
          messageSubscription.cancel();
          closeSubscription.cancel();
          poll = null;
  