chromium/third_party/blink/web_tests/external/wpt/html/semantics/embedded-content/the-embed-element/embed-change-src.html

<!DOCTYPE html>
<html class="reftest-wait">
<meta charset="utf-8">
<link rel="author" title="Joey Arhar" href="mailto:[email protected]">
<link rel="help" href="https://html.spec.whatwg.org/multipage/iframe-embed-object.html#the-embed-element">
<link rel="help" href="http://crbug.com/1035330">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<body>
<script>
promise_test(async () => {
  const embed = document.createElement('embed');
  let loadPromise = new Promise(resolve => embed.onload = resolve);
  embed.src = '/media/white.mp4';
  document.body.appendChild(embed);

  await loadPromise;

  loadPromise = new Promise(resolve => embed.onload = resolve);
  embed.src = '/media/white.webm';

  await loadPromise;
}, 'Verifies that embed elements reload with new content when the src attribute is changed.');
</script>