preload-link-cached-stylesheet-different-doc.html

<!doctype html>
<meta charset="utf-8">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1646776">
<link rel="author" href="mailto:[email protected]" title="Emilio Cobos Álvarez">
<link rel="author" href="https://mozilla.org" title="Mozilla">
<link rel="stylesheet" href="data:text/css,:root{background:green}">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<body>
<script>
  // Note that script execution waits for the stylesheet above to be loaded.
  window.t = async_test("Stylesheets that are already loaded in the document don't cause spurious error events on preloads");
  let subdoc = document.createElement("iframe");
  subdoc.srcdoc = `
    <!doctype html>
    <meta charset="utf-8">
    <link rel="preload" as="style" href="data:text/css,:root{background:green}" onload="parent.t.done()" onerror="parent.t.step(() => parent.assert_unreached('should not error'))">
  `;
  document.body.appendChild(subdoc);
</script>

chromium/third_party/blink/web_tests/external/wpt/preload/preload-link-cached-stylesheet-different-doc.html