dispose method
Called when its corresponding element disposed
Implementation
@override
void dispose() {
  super.dispose();
  _outerClipLayer.layer = null;
  _innerClipLayer.layer = null;
  _transformLayer.layer = null;
}Called when its corresponding element disposed
@override
void dispose() {
  super.dispose();
  _outerClipLayer.layer = null;
  _innerClipLayer.layer = null;
  _transformLayer.layer = null;
}