title: onaddstream event not called
body: <p>I use WebRTC to connected 2 Chrome Browsers. I create <code>offer</code> on the first and send it via <code>signalR</code> to second client like this :</p>
  
  <pre><code>function initiate_call() {
  callerPeerConn = new RTCPeerConnection(peerConnCfg);
  callerPeerConn.ontrack = function (event) {
      console.log('caller recived new stream');
      remoteVideo.srcObject = event.streams[0];
      console.log(event);
  }
  navigator.mediaDevices.getUserMedia({ audio: true, video: true })
      .then(function (stream) {
          localVideo.srcObject = stream;
          for (const track of stream.getTracks()) {
              callerPeerConn.addTrack(track, stream);
          }
          return callerPeerConn.createOffer();
      })
      .then(
      function (offer) {
          var off = new RTCSessionDescription(offer);
          callerPeerConn.setLocalDescription(
              new RTCSessionDescription(off),
              function () {
                  // invite to video chat
                  console.log('send offer');
              },
              function (err) {
                  console.log(err.message);
              }
          )
      });
  }
  </code></pre>
  
  <p>When my second browser getting <code>offer</code> he use <code>setLocalDescription</code> and try to create <code>answer</code> than send it to caller like that :</p>
  
  <pre><code>function accept_send_answer(){    
  calleePeerConn = new RTCPeerConnection(peerConnCfg);
  calleePeerConn.ontrack = function (event) {
      console.log('callee accept offer and got streams');
      remoteVideo.srcObject = event.streams[0];
  }
  calleePeerConn.setRemoteDescription(offer)
      .then(function () {
          return navigator.mediaDevices.getUserMedia({ audio: true, video: true });
      })
      .then(function (stream) {
          localVideo.srcObject = stream; 
  
          for (const track of stream.getTracks()) {
              calleePeerConn.addTrack(track, stream);
          }
          return calleePeerConn.createAnswer();
      })
      .then(function (answer) {
          // sending answer
  
          console.log("sending ansfer");
          var remote_streams = calleePeerConn.getRemoteStreams();
          var local_streams = calleePeerConn.getLocalStreams();
  
          console.log("callee remote streams");
          console.log(remote_streams);
          console.log("callee local streams");
          console.log(local_streams);
      })
      .catch(function (err) {
          console.log(err.message);
      });
  }
  </code></pre>
  
  <h1>UPD</h1>
  
  <p>After I changed my code, following the advice of a respected @jib, my local and remote streams on both sides was successfully added to RTCPeerConnection object. I successfully obtain following messanges in console : <code>caller recived new stream</code> and  <code>callee accept offer and got streams</code> as well. Last problem is - why this code not working :</p>
  
  <pre><code>calleePeerConn.ontrack = function (event) {
      console.log('callee accept offer and got streams');
      remoteVideo.srcObject = event.streams[0];
  }
  </code></pre>
  
  <p>video not played. </p>