overlay-scrollbar-over-child-layer.html

<!DOCTYPE html>
<script>
if (window.internals)
  internals.useMockOverlayScrollbars();
</script>
<div id="container" style="width: 200px; height: 200px; overflow: scroll">
  <div id="content" style="position: relative; background: green; width: 300px; height: 100px"></div>
  <div style="height: 210px"></div>
</div>

chromium/third_party/blink/web_tests/scrollbars/overlay-scrollbar-over-child-layer.html