document-render-blocking-no-block.html

<!DOCTYPE html>
  <html>
  <script src="../../resources/gc.js"></script>
  <script src="../../resources/testharness.js"></script>
  <script src="../../resources/testharnessreport.js"></script>
  <title>Absence of blocking doesn't defer frames until complete document parsed</title>
  <script>
    function jank(ms) {
      let start = performance.now();
      while (performance.now() < start + ms);
    }

    function jankMany(ms, times) {
      for (let i = 0; i < times; i++) {
        jank(ms);
      }
    }
    promise_test(() => {
      return new Promise((resolve, reject) => {
        requestAnimationFrame(() => {
          if (document.getElementById("last"))
            reject();
          else
            resolve();
        });
      });
    }, "frames not deferred until full parsing");
  </script>
  </head>
  <body>
    <div id="first"></div>
    <script>
      jankMany(100, 10);
    </script>
    <div id="second"></div>
    <script>
      jankMany(100, 10);
    </script>
    <div id="last"></div>
  </body>
</html>

chromium/third_party/blink/web_tests/dom/domparsing/document-render-blocking-no-block.html