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chromium/third_party/blink/web_tests/http/tests/media/video-progress-mediastream.html 

<!DOCTYPE html>
<title>Test that the "progress" event is not fired periodically for a MediaStream.</title>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<video></video>
<script>
async_test(function(t) {
  var video = document.querySelector("video");

  var num_progress = 0;
  video.onprogress = () => { num_progress += 1; };

  // Wait 1.5 second from the first frame to ensure that the "progress" event
  // is not fired more than once.
  video.requestVideoFrameCallback(() => {
    setTimeout(t.step_func_done(() => {
      assert_equals(num_progress, 1);
    }), 1500);
  })

  navigator.mediaDevices.getUserMedia({ video: true }).then(function (stream) {
    video.srcObject = stream;
    video.play();
  }, t.unreached_func("getUserMedia failed"));
});
</script>