scrollbar-painting.html | Explore in Territory

<!DOCTYPE html>
<style>
.composited {
  will-change: transform;
}

.container {
  width:100px;
  height:100px;
  overflow:scroll;
  resize:both;
  position:absolute;
}

.container::-webkit-scrollbar {
  background-color: rgba(0, 127, 0, 0.5);
}

.container::-webkit-resizer {
  background-color: rgba(0, 127, 0, 0.5);
}

.contents {
  background-color: rgba(0, 127, 0, 0.5);
  height: 100%;
  width: 100%;
}
</style>
<!-- You should see a single 50% transparent green square -->
<div id="container" class="container composited">
  <div class="contents"></div>
</div>

chromium/third_party/blink/web_tests/compositing/scrollbar-painting.html