anchor.diff:        onPointerCancel: _handlePointerUpOrCancel,
         onGestureFlingStart: _handleFlingStart,
         child: new SizeObserver(
  -        child: transformedChild,
  -        callback: _handleSizeChanged
  +        callback: _handleSizeChanged,
  +        child: new Opacity(
  +          opacity: _opacity.value,
  +          child: new Transform(
  +            transform: transform,
  +            child: child
  +          )
  +        )
         )
       );
     }
  
positive.code:       _dragUnderway = false;
        double distance = 1.0 - _performance.progress;
        if (distance > 0.0) {
          double duration = _kCardDismissFadeoutMS * 1000.0 * distance / event.velocityX.abs();
          _dragX = event.velocityX.sign;
          _performance.timeline.animateTo(1.0, duration: duration);
        }
  
negative.code: 
    void _handleSizeChanged(Size newSize) {
      _width = newSize.width;
      _position.end = _activeCardDragEndPoint;
    }
  
    void _handlePointerDown(sky.PointerEvent event) {
  