Bug 1259788 - Can't MediaRecord a video.mozCaptureStream with gum src

MEDIA_ERR_SRC_NOT_SUPPORTED

by jib1

HTML

<video id="video1" height="120" width="160" autoplay></video>
<video id="video2" height="120" width="160" controls autoplay></video><br>
<button onclick="start(3000)">Record!</button>
<a id="link"></a><div id="div"></div><br>

JavaScript

var start = ms => navigator.mediaDevices.getUserMedia({ video: true })
//.then(stream => record(stream, ms).then(r => new Blob(r)))
  .then(stream => {
    video1.src = URL.createObjectURL(stream);
    link.href = stream;
    return new Promise(resolve => video1.onplaying = resolve);
  })
  .then(() => record(video1.mozCaptureStreamUntilEnded(), ms))
  .then(recording => {
    video2.src = link.href = URL.createObjectURL(new Blob(recording));
    link.download = "recording.blob";
    link.innerHTML = "Download blob";
    log("Successfully recorded "+ recording[0].size +" byte blob");
    log("Playing "+ recording[0].type +" recording.");
    return new Promise((resolve, reject) => {
      video2.onplaying = resolve;
      video2.onerror = e => reject((e.target.error.code == 4)? 
        "MEDIA_ERR_SRC_NOT_SUPPORTED" : e.target.error.code);
    });
  })
  .catch(log);

var record = (stream, ms) => {
  var rec = new MediaRecorder(stream), data = [];
  rec.ondataavailable = e => data.push(e.data);
  rec.start();
  log(rec.state + " for "+ (ms / 1000) +" seconds...");
  var stopped = new Promise((r, rej) => (rec.onstop = r,
                                         rec.onerror = e => rej(e.name)));
  return Promise.all([
      stopped,
      wait(ms).then(() => rec.state == "recording" && rec.stop())
    ])
    .then(() => data);
};

var stop = stream => stream.getTracks().forEach(track => track.stop());
var wait = ms => new Promise(resolve => setTimeout(resolve, ms));
var log = msg => div.innerHTML += "<br>" + msg;