css/css-scroll-anchoring/nested-overflow-subtree-layout.html

<!DOCTYPE html>
<html class="reftest-wait">
<head>
  <title>Test that subtree layout with nested overflow preserves scroll anchoring.</title>
  <link rel="author" title="Chris Harrelson" href="mailto:chrishtr@chromium.org">
  <link rel="help" href="https://drafts.csswg.org/css-scroll-anchoring/">
  <link rel="match" href="nested-overflow-subtree-layout-ref.html">
  <script src="/common/reftest-wait.js"></script>
</head>
<style>
#outer {
  overflow: hidden;
  width: 500px;
  height: 500px;
}
#inner {
  overflow: auto;
  position: relative;
  width: 500px;
  height: 2000px;
}
p {

  font: 48pt monospace;
}
</style>
</head>
<body>
<div id="outer">
  <div id="inner">
    <p>Anchor</p>
  </div>
</div>
<script>
const outer = document.querySelector("#outer");
const inner = document.querySelector("#inner");

onload = () => {
  requestAnimationFrame(() => {
    requestAnimationFrame(() => {
      outer.scrollTo(0, 70);
      requestAnimationFrame(() => {
          const elem = document.createElement("p");
          elem.textContent = "FAIL";
          inner.insertBefore(elem, inner.firstChild);
          takeScreenshot();
      });
    });
  });
};
</script>