fixed-position-out-of-view-scroll-reason.html

<!DOCTYPE html>

<html>
<head>
<style>
  .fixed {
    position: fixed;
    width: 10px;
    height: 10px;
    z-index: -1;
    background-color: silver;
  }
</style>

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

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

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

<body>
<div style="height: 1000px">
  Main thread scrolling reasons should be blank:
  <pre id="mainThreadScrollingReasons"></pre>
</div>

<!-- out of view fixed position elements should not trigger main thread scrolling. -->
<div class="fixed"></div>
<div class="fixed" style="top: -100px"></div>
<div class="fixed" style="top: 0px; left: 1000px"></div>

</body>
</html>

chromium/third_party/blink/web_tests/compositing/layer-creation/fixed-position-out-of-view-scroll-reason.html