chromium/third_party/blink/web_tests/external/wpt/css/css-masking/clip-path/clip-path-filter-order.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Clip-path should be applied after filtering</title>
<link rel="author" title="Philip Rogers" href="mailto:[email protected]">
<link rel="help" href="https://drafts.fxtf.org/css-masking-1/#placement">
<link rel="match" href="clip-path-filter-order-ref.html">

<div>
  <p>Expected: A green box.<br>
  There should be no red visible.<br>
  There should be a crisp, clipped edge around the green box (no blurring).</p>
</div>

<style>
  #testcase {
    position: absolute;
    width: 400px;
    height: 400px;
    background: green;
    will-change: transform;
    filter: drop-shadow(16px 16px 20px red);
    clip-path: inset(0px 200px 200px 0px);
  }
</style>
<div id="testcase"></div>