copy method
Copies another name object to this instance.
Implementation
@override
CurvePath copy(Curve source) {
  assert(source is CurvePath);
  super.copy(source);
  curves = [];
  for (int i = 0, l = source.curves.length; i < l; i++) {
    final curve = source.curves[i];
    curves.add(curve.clone());
  }
  autoClose = source.autoClose;
  return this;
}