css/css-scroll-anchoring/focused-element-outside-scroller.html

<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-scroll-anchoring/">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>

body { height: 4000px; }
div { height: 100px; }

.scroller {
  overflow: scroll;
  position: fixed;
  width: 300px;
  height: 300px;
  background-color: green;
}

#content {
  background-color: #D3D3D3;
  height: 50px;
  width: 50px;
  position: relative;
  top: 500px;
}

</style>
<div id="scroller" class="scroller">
  <div id="content"></div>
</div>
<div id="block1" tabindex="-1">abc</div>

<script>

// Tests that a focused element doesn't become the
// priority candidate of the subscroller

promise_test(async function() {
  var scroller = document.querySelector("#scroller");
  var focusElement = document.querySelector("#block1");
  focusElement.focus();
  scroller.scrollBy(0,150);
  document.scrollingElement.scrollBy(0,100);
  await new Promise(resolve => {
     document.addEventListener("scroll", () => step_timeout(resolve, 0));
   });

  assert_equals(scroller.scrollTop, 150);
}, "Ensure there is no scroll anchoring adjustment in subscroller.");

</script>