[RTCPeerConnection-addTrack.https.html]
  [addTrack with single track argument and no mediaStream should succeed]
    expected: FAIL

  [addTrack with existing sender with null track, same kind, and recvonly direction should reuse sender]
    expected: FAIL

  [addTrack with existing sender with null track, same kind, and sendrecv direction should create new sender]
    expected: FAIL

  [addTrack with existing sender with null track, different kind, and recvonly direction should create new sender]
    expected: FAIL