<!DOCTYPE html>
<meta charset="utf-8">
<link rel=author href="mailto:xiaochengh@chromium.org">
<link rel=help href="https://open-ui.org/components/popover.research.explainer">
<link rel=help href="https://html.spec.whatwg.org/multipage/popover.html">

<button id=main-menu-button>Show menu</button>

<div id=main-menu>
  <div>Foo</div>
  <button id=nested-menu-button>
    Show nested menu
  </button>
  <div>Bar</div>
</div>

<div id=nested-menu>
  Baz
</div>

<style>
#main-menu-button {
  position: absolute;
  top: 200px;
  left: 100px;
  width: 100px;
}

#main-menu {
  position: absolute;
  top: 200px;;
  left: 200px;
  width: 150px;
  line-height: 20px;
}

#nested-menu-button {
  width: 100%;
}

#nested-menu {
  position: absolute;
  top: 220px;
  left: 350px;
}

[popover] {
  border: 0;
  margin: 0;
  padding: 0;
}
</style>

<script>
document.getElementById('main-menu-button').click();
document.getElementById('nested-menu-button').click();
</script>
