<!DOCTYPE HTML>
<style>
  #scroller {
    overflow: scroll;
    width: 300px;
    height: 300px;
    position: relative;
    z-index: 0;
    top: 10px;
  }

  #fixed {
    position: fixed;
    background: blue;
    left: 90px;
    width: 10px;
    height: 10px;
  }

  #scrolled {
    position: relative;
    background: green;
    width: 80px;
    height: 500px;
  }
</style>
<script>
if (window.internals) {
    window.internals.settings.setOverlayScrollbarsEnabled(true);
    window.internals.settings.setPreferCompositingToLCDTextEnabled(false);
}
</script>
<div id='scroller'>
  <div id='fixed'></div>
  <div id='scrolled'></div>
</div>