private void addExtendedRuleDropdown( Collection<String> ruleNames ) {
layout.setWidget( currentLayoutRow,
0,
new SmallLabel( "<b>" + Constants.INSTANCE.EXTENDS() + "</b>" ) );
RuleSelector ruleSelector = new RuleSelector( ruleNames, model.name );
ruleSelector.setRuleName( model.parentName );
ruleSelector.addValueChangeHandler( new ValueChangeHandler<String>() {
@Override
public void onValueChange( ValueChangeEvent<String> event ) {
model.parentName = event.getValue();
}
} );