1. override
void debugFillDescription(List<String> description)

Accumulates a list of strings describing the current node's fields, one field per string. Subclasses should override this to have their information included in toStringDeep.

Source 

@override
void debugFillDescription(List<String> description) {
  super.debugFillDescription(description);
  if (maxWidth != double.INFINITY)
    description.add('maxWidth: $maxWidth');
  if (maxHeight != double.INFINITY)
    description.add('maxHeight: $maxHeight');
}