css/css-overflow/overflow-abpos-transform.html

<!DOCTYPE html>
<title>CSS Overflow and Transforms: css-overflow-3</title>
<link rel="author" title="mailto:atotic@google.com">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="help" href="https://www.w3.org/TR/css-overflow-3/#scrollable">
<meta name="assert" content="css transform is used to compute scroll overflow of abspos children">
<style>
  #container {
    position: relative;
    overflow: auto;
    width: 200px;
    height: 200px;
  }
  #target {
    position: absolute;
    width: 150px;
    height: 150px;
    margin-left: 100px;
    transform: translateX(-100px);
    background: green;
  }
</style>
<!-- There should be no scrollbars on this page -->
<div id="container">
  <div id="target"></div>
</div>
<script>
  test(() => {
    assert_equals(document.querySelector("#container").scrollWidth, 200);
  }, '#target used transform when computing scroll overflow');
</script>