anchor.diff:    bool _addTimerToHeap() {
       if (_wakeupTime == 0) {
         if (_firstZeroTimer == null) {
  -        _lastZeroTimer = _firstZeroTimer = this;
  +        _lastZeroTimer = this;
  +        _firstZeroTimer = this;
           return true;
         } else {
  -        _lastZeroTimer = _lastZeroTimer._indexOrNext = this;
  +        _lastZeroTimer._indexOrNext = this;
  +        _lastZeroTimer = this;
           return false;
         }
       } else {
  
positive.code:     // Collect all pending timers.
      var timer = _firstZeroTimer;
      var nextTimer = _lastZeroTimer;
      _firstZeroTimer = _lastZeroTimer = null;
      while (_heap.isNotEmpty && _heap.first._wakeupTime <= currentTime) {
        var next = _heap.removeFirst();
        if (timer == null) {
          nextTimer = timer = next;
        } else {
          nextTimer = nextTimer._indexOrNext = next;
        }
      }
  
  
negative.code:     _clear();
      if (!_isInHeap) return;
      assert(_wakeupTime != 0);
      bool update = (_firstZeroTimer == null) && _heap.isFirst(this);
      _heap.remove(this);
      if (update) {
        _notifyEventHandler();
  