1. DomName('MessagePort.postMessage')
  2. DocsEditable()
void postMessage(Object message, [List<MessagePort> transfer])

Source 

@DomName('MessagePort.postMessage')
@DocsEditable()
void postMessage(Object message, [List<MessagePort> transfer]) => _blink.BlinkMessagePort.instance.postMessage_Callback_2_(unwrap_jso(this), convertDartToNative_SerializedScriptValue(message), transfer);