html/rendering/non-replaced-elements/the-fieldset-and-legend-elements/fieldset-dynamic-baseline.html

<!DOCTYPE html>
<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1307140">
<link rel="match" href="fieldset-dynamic-baseline-ref.html">
baseline
<fieldset style="display: inline-block;">
  <div style="position: relative;">
    line1<br>line2<div id="target" style="position: absolute;"></div>
  </div>
</fieldset>
<script>
document.body.offsetTop;
document.getElementById('target').style.top = '10px';
</script>