createOffer method

Future<RtcSessionDescription> createOffer ([Map mediaConstraints ])

Implementation 

Future<RtcSessionDescription> createOffer([Map mediaConstraints]) {
  var completer = new Completer<RtcSessionDescription>();
  _createOffer((value) {
    completer.complete(value);
  }, (error) {
    completer.completeError(error);
  }, mediaConstraints);
  return completer.future;
}