anchor.diff:  abstract class Votable {
   
     final Element elem;
  -  final List<StreamSubscription> _clickSubscriptions = [];
   
     StateMachine _machine;
     int _currentCount;
  
positive.code:       _machine.processTrigger(
            new _VotableTrigger()
              ..downVoting = true);
      }));
    }
  
    void _unregisterClick() {
      _clickSubscriptions.forEach((sub) => sub.cancel());
      _clickSubscriptions.clear();
    }
  
    void _changeCount({int delta}) {
  
negative.code:       _machine.processTrigger(
            new _VotableTrigger()
              ..upVoting = true);
      });
      _downVoteElem.onClick.listen((e) {
        e
          ..stopPropagation()
          ..preventDefault();
  