chromium/third_party/blink/web_tests/external/wpt/html/semantics/embedded-content/media-elements/ready-states/autoplay-hidden.optional.html

<!doctype html>
<title>autoplay hidden</title>
<link rel="author" title="Intel" href="http://www.intel.com">
<link rel="help" href="https://html.spec.whatwg.org/multipage/media.html#ready-states"/>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/common/media.js"></script>
<div id="log"></div>
<script>

// https://html.spec.whatwg.org/multipage/media.html#ready-states:eligible-for-autoplay-2

promise_test(async t => {
  let video = document.createElement("video");
  video.src = getVideoURI("/media/movie_5");
  video.autoplay = true;
  // In Safari, Chrome and Firefox, the video needs to be muted in order to be
  // paused when hidden. They decided to do this in order to save resources when
  // a video goes out of view and isn't expected to make any sound.
  video.muted = true;
  video.loop = true;
  let watcher = new EventWatcher(t, video, ["playing", "pause"]);
  document.body.appendChild(video);

  await watcher.wait_for("playing");
  assert_false(video.paused, "paused when video is display");
  video.hidden = true;

  await watcher.wait_for("pause");
  assert_true(video.paused, "paused when video is hidden");
  video.hidden = false;

  await watcher.wait_for("playing");
  assert_false(video.paused, "paused when video is display");
}, "Allow delaying autoplay until video elements become visible");

</script>