no-compositing-for-fixed-position-under-transform.html

<!DOCTYPE html>
<html>
<head>
  <style>
    .transform {
      width: 100px;
      height: 30px;
      background: blue;
      will-change: transform;
    }
    .fixed {
      position: fixed;
      left: 10px;
      top: 10px;
    }
  </style>

  <script type="text/javascript">
    if (window.internals) {
      internals.settings.setPreferCompositingToLCDTextEnabled(true);
    }

    if (window.testRunner) {
      testRunner.dumpAsText();

      window.addEventListener("load", function() {
        document.getElementById("layerTree").innerText = internals.layerTreeAsText(document);
        document.getElementById("mainThreadScrollingReasons").innerText = internals.mainThreadScrollingReasons(document);
      }, false);
    }
  </script>
</head>

<body>
  <div class="transform">
    <!-- This element should neither be composited nor force main thread scrolling. -->
    <div class="fixed">TEST</div>
  </div>

  <pre id="layerTree"></pre>
  <pre id="mainThreadScrollingReasons"></pre>
</body>
</html>

chromium/third_party/blink/web_tests/compositing/layer-creation/no-compositing-for-fixed-position-under-transform.html