);
}
#top-backdrop {
    top: 150px;
    left: 150px;
    background-color: rgb(0, 210, 0);
}
.fake-popover {
  margin:0;
}
</style>
<p>Test for [popover]::backdrop presence and stacking order. The test passes
  if there are 3 stacked boxes, with the brightest green on top.</p>
<div popover id=bottom>Bottom
  <div popover id=middle>Middle
    <div popover=manual id=top>Top</div>
  </div>
</div>
<div id="bottom-backdrop" class="fake-popover-backdrop"></div>
<div id="bottom" class="fake-popover">Bottom</div>
