Multi-streams attachment in RTCMultiConnection-v1.4 added

You can easily stream audio/video along with screen (using single peer
connection):

connection.session = {
---- audio: true,
---- video: true,
---- screen: true,
---- oneway: true
};

Demo:

https://webrtc-experiment.appspot.com/RTCMultiConnection-v1.4-Demos/multi-streams-attachment.html