void generateKeyRequest(String keySystem, [Uint8List initData])

Source 

void generateKeyRequest(String keySystem, [Uint8List initData]) {
  if (initData != null) {
    _blink.BlinkHTMLMediaElement.instance.webkitGenerateKeyRequest_Callback_2_(this, keySystem, initData);
    return;
  }
  _blink.BlinkHTMLMediaElement.instance.webkitGenerateKeyRequest_Callback_1_(this, keySystem);
  return;
}