root-element-background-transparency.html

<!doctype HTML>
<style>
html::-webkit-scrollbar {
    display:none;
}
</style>
<!-- This is the same test as external/wpt/css/compositing/root-element-background-transparency.html.
It is duplicated here because it's not clear how to make it a reftest successfully and avoid
alpha-channel diffs, and fuzzy matching doesn't seem to work for that channel. -->
<html style="background: rgba(45, 45, 45, 0.5);">
  <div id=spacer style="width: 100px; height: 3000px"></div>
</html>

chromium/third_party/blink/web_tests/paint/background/root-element-background-transparency.html