anchor.diff:    static const int framePendingFlag = 1 << 2;
   
     int flags = 0;
  -  int clock = 0;
  +  int clock = 1;
   
     bool get isRunning => ((flags & runningFlag) != 0);
   
  
positive.code:     _zone.run(() {
        flags &= ~framePendingFlag;
        flags |= runningFlag;
        clock++;
  
        _nextTickCompleter.complete();
        _nextTickCompleter = null;
  
negative.code:       _handleNextTick();
      }
    }
  
    void run(fn) {
      _zone.run(() {
        flags |= runningFlag;
  
        fn();
  
        clock++;
        flags &= ~runningFlag;
      });
    }
  }
  