void addStream(MediaStream stream, [ Map mediaConstraints ])

Source 

void addStream(MediaStream stream, [Map mediaConstraints]) {
  if (mediaConstraints != null) {
    _blink.BlinkRTCPeerConnection.instance.addStream_Callback_2_(
        this, stream, convertDartToNative_Dictionary(mediaConstraints));
    return;
  }
  _blink.BlinkRTCPeerConnection.instance.addStream_Callback_1_(this, stream);
  return;
}