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