<!DOCTYPE html>
<html>
<head>
<style>
  body {
    width: 1000px;
    height: 800px;
  }
  .reference {
    position: absolute;
    left: 51px;
    top: 51px;
    width: 98px;
    height: 98px;
    background-color: blue;
  }
  .fixed {
    position: fixed;
    left: 50px;
    top: 50px;
    width: 100px;
    height: 100px;
    background-color: white;
  }
</style>
<script>
  if (window.internals) {
    window.internals.settings.setAcceleratedCompositingForFixedPositionEnabled(true);
    window.internals.settings.setFixedPositionCreatesStackingContext(true);
    window.internals.setPageScaleFactor(0.5, 0, 0);
  }
</script>
</head>
<body>
  On success, the blue reference box should be invisible (covered by the fixed box).
  <div class="reference"></div>
  <div class="fixed"></div>
</body>
</html>