getClip method
- Size size
override
    Returns a description of the clip given that the render object being clipped is of the given size.
Implementation
@override
Path getClip(Size size) {
  var path = Path();
  path.lineTo(0, size.height - 100);
  path.quadraticBezierTo(
      size.width / 2, size.height, size.width, size.height - 100);
  path.lineTo(size.width, 0);
  path.close();
  return path;
}