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chromium/third_party/blink/web_tests/shadow-dom/focus-navigation/focus-scroller-layout-update.html 

<!DOCTYPE html>
<script src='../../resources/testharness.js'></script>
<script src='../../resources/testharnessreport.js'></script>
<script src='../resources/focus-utils.js'></script>

<!-- Note: Do not move this test to WPT, as "keyboard focusable scrollers"
     does not have standard behavior across browsers. -->
<button id="button">Button</button>
<div id="scroller" style="overflow:scroll; width:50px; height:50px;">
  <div style="height:100px"></div>
</div>

<script>
promise_test(async () => {
  const button = document.getElementById('button');
  const scroller = document.getElementById('scroller');

  scroller.focus();
  assert_equals(document.activeElement, scroller);

  button.focus();
  assert_equals(document.activeElement, button);

  scroller.style.height = '200px';
  scroller.focus();
  assert_equals(document.activeElement, button, 'Should not focus on scroller since it is no longer scrollable');
}, 'When checking that element is a scroller, layout information should be up to date.');
</script>