css/css-overflow/dynamic-visible-to-clip-001.html

<!doctype html>
<html class="reftest-wait">
<meta charset="utf-8">
<title>Overflow areas are updated when dynamically changed to overflow: clip</title>
<link rel="help" href="https://drafts.csswg.org/css-overflow/#valdef-overflow-clip">
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="author" title="Mozilla" href="https://mozilla.org">
<link rel="match" href="clip-001-ref.html">
<style>
  #target {
    width: 100px;
    height: 100px;
    overflow: visible;
  }

  #container {
    overflow: auto;
    height: 300px;
  }
  #fill {
    height: 5000px;
    background: blue;
  }
</style>
<div id="container">
  <div id="target">
    <div id="fill"></div>
  </div>
</div>
<script>
onload = function() {
  let target = document.getElementById("target");
  window.unused = target.getBoundingClientRect(); // Update layout
  requestAnimationFrame(() => requestAnimationFrame(() => {
    target.style.overflow = "clip";
    document.documentElement.removeAttribute("class");
  }));
}
</script>