anchor.diff:        _startResizePerformance();
     }
   
  -  Point get _activeCardDragEndPoint {
  -    if (!_isActive)
  -      return Point.origin;
  -    assert(_size != null);
  -    double extent = _directionIsYAxis ? _size.height : _size.width;
  -    return new Point(_dragExtent.sign * extent * _kDismissCardThreshold, 0.0);
  -  }
  -
     bool get _isActive {
       return _size != null && (_dragUnderway || _fadePerformance.isAnimating);
     }
  
positive.code:         break;
      }
  
      if (oldDragExtent.sign != _dragExtent.sign)
        setState(() {}); // Rebuild to update the new drag endpoint.
      if (!_fadePerformance.isAnimating)
        _fadePerformance.progress = _dragExtent.abs() / (_size.width * _kDismissCardThreshold);
    }
  
negative.code:   void _handleDragStart() {
      if (_fadePerformance.isAnimating)
        return;
      setState(() {
        _dragUnderway = true;
        _dragExtent = 0.0;
        _fadePerformance.progress = 0.0;
      });
    }
  
    void _handleDragUpdate(double scrollOffset) {
  