<!DOCTYPE html>

<html>
<head>
<style>
  .fixed {
    position: fixed;
    width: 50px;
    height: 50px;
    top: 10px;
    left: 10px;
    z-index: -1;
  }
</style>

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

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

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

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