chromium/third_party/blink/web_tests/external/wpt/html/semantics/embedded-content/the-embed-element/embed-document-under-content-visibility-focus.html

<!doctype html>
<meta charset="utf-8">
<title>HTML Test: The embed element represents a document</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<meta name="assert" content="Ensure document finishes load when focus is attempted before the embed is finished loading">

<style>
.hidden { content-visibility: hidden; }
</style>
<body>
  <script>
  async_test(t => {
    window.onload = () => t.done();
  }, "ensure onload happens");
  </script>
  <div class=hidden>
    <embed id=target src="embed-iframe.html">
  </div>
  <script>
    // Ensure we process style in the hidden object, which normally delays
    // load until the embed object is finished loading.
    target.focus();
  </script>
</body>