LayoutTests/fast/block/containing-block-for-out-of-flow-becomes-static.html

<style>
.boundary {
  overflow: hidden;
  width: 500px;
  height: 200px;
}

#relpos {
  position: relative;
  border: 100px solid green;
}

#abspos {
  position: absolute;
  left: 0px;
  top: 0px;
}
</style>
<div style="position: relative;">
  <div class=boundary>
    <div id=relpos>
      <div id=abspos>PASS if this text is at the top left corner of the green box.</div>
    </div>
  </div>
</div>
<script>
document.body.offsetHeight;
relpos.style.position="static";
</script>