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);
  description.add('direction: $_direction');
  description.add('mainAxisAlignment: $_mainAxisAlignment');
  description.add('mainAxisSize: $_mainAxisSize');
  description.add('crossAxisAlignment: $_crossAxisAlignment');
  description.add('textBaseline: $_textBaseline');
}