MediaStreamManager#acquire takes mediaHint, returns Promise
WebRTC.MediaHandler#getDescription takes mediaHint, returns Promise
WebRTC.MediaHandler#setDescription takes sdp, returns Promise
Session, WebRTC.MediaStreamManager: Put '.then(' on own line
WebRTC.MediaHandler#addStream returns a promise
WebRTC.MediaHandler#getDescription: define streamAdditionSucceeded later
WebRTC.MediaHandler#getDescription: fix indentation of previous commit