<!DOCTYPE html>
<style>
  /* Prevent auto viewport overflow, because that would trigger another
     layout pass, hiding the bug. */
  body { overflow:hidden; }
</style>
<p>There should be a green square below. No red, orange or yellow.</p>
<!-- The outer container is there to clip painting of the scrollbar,
     to make it easier to write a reftest. -->
<div style="overflow:hidden; width:50px; height:50px; background:orange;">
  <!-- The overflow:auto block needs auto width to be able to
       reproduce the bug. Use a wide wrapper, so that the scrollbar
       gets clipped. -->
  <div style="width:100px; background:red;">
    <div style="overflow:auto; height:50px; background:yellow;">
      <div style="height:51px; background:green;"></div>
    </div>
  </div>
</div>