chromium/third_party/blink/web_tests/external/wpt/css/css-position/backdrop-inherit-rendered.html

<!DOCTYPE html>
<title>CSS Position Test: ::backdrop inherits from originating element - rendering</title>
<link rel="help" href="https://drafts.csswg.org/css-position-4/#backdrop">
<link rel="match" href="backdrop-inherit-rendered-ref.html">
<style>
  dialog {
    --bg: green;
    inset: 100px;
  }
  dialog::backdrop {
    background-color: var(--bg);
    inset: inherit;
  }
</style>
<dialog>Green backdrop with 100px inset</dialog>
<script>
  document.querySelector("dialog").showModal();
</script>