切換RTCPeerConnection的stream

//删除原有的stream
rtcPeerConnection.removeStream(localStream);
//加入新的stream
rtcPeerConnection.addStream(screenshootStream);
//重新發送offer
createOffer(k,peerList[k]);
           

學習自：

https://stackoverflow.com/questions/24239522/changing-a-mediastream-of-rtcpeerconnection