1. DomName('HTMLOutputElement.setCustomValidity')
  2. DocsEditable()
void setCustomValidity(String error)

Source 

@DomName('HTMLOutputElement.setCustomValidity')
@DocsEditable()
void setCustomValidity(String error) => _blink.BlinkHTMLOutputElement.instance.setCustomValidity_Callback_1_(unwrap_jso(this), error);