WebRTC.getUserMedia returns a Promise if only constraints are given
MediaStreamManager#acquire takes mediaHint, returns Promise
WebRTC.MediaHandler#getDescription takes mediaHint, returns Promise
WebRTC.MediaHandler#setDescription takes sdp, returns Promise
WebRTC.MediaHandler: remove onSuccess/onFailure comments from get/setDescription
WebRTC.MediaHandler#getDescription: move acquireSucceeded into promise chain
Session: clean up whitespace in promise chains
Session: remove trival comments from SDP promise chains