css/css-scrollbars/auto-scrollbar-inline-children.html

<!DOCTYPE html>
<link rel="author" title="Morten Stenshorne" href="mstensho@chromium.org">
<link rel="help" href="https://www.w3.org/TR/CSS22/visufx.html#propdef-overflow">
<style>
  /* Avoid auto scrollbars on the viewport, because that might trigger re-layout
    (and thus hide bugs). */
  body { overflow:hidden; }

  .container { width:100px; }
</style>
<p>There should be a blue rectangle below, and possibly a scrollbar (depending
  on OS / browser), that shouldn not obscure any parts of the rectangle. The
  word "FAIL" should not be seen.</p>
<div class="container" style="overflow:auto; height:200px;">
  <div id="child" style="display:inline-block; box-sizing:border-box; width:100%; height:100%; border:10px solid blue;"></div>
  <br>FAIL
</div>

<div class="container" style="visibility:hidden; overflow:scroll;">
  <div id="ref"></div>
</div>

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
  test(()=> {
    var child = document.getElementById("child");
    assert_equals(child.offsetWidth, ref.offsetWidth);
  }, "Auto scrollbar affects size of children");
</script>