chromium/third_party/blink/web_tests/external/wpt/css/filter-effects/backdrop-filter-basic.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>backdrop-filter: Basic operation of filter</title>
<link rel="author" href="mailto:[email protected]">
<link rel="help" href="https://drafts.fxtf.org/filter-effects-2/#BackdropFilterProperty">
<link rel="match"  href="backdrop-filter-basic-ref.html">

<div>
  <p>Expected: A green box and an overlapping black box, with a magenta<br>
  overlapping region.</p>
</div>
<div class="colorbox">
  <div class="filterbox"></div>
</div>

<style>
.colorbox {
    position: absolute;
    background: green;
    width: 100px;
    height: 100px;
    left: 10px;
    top: 100px;
}
.filterbox {
    position: absolute;
    width: 100px;
    height: 100px;
    left: 50px;
    top: 50px;
    backdrop-filter: invert(1);
    opacity: 1.0;
}
</style>