LayoutTests/fast/ruby/ruby-underline-decoration-stretch.html

<style>
div {
  font-family: Ahem;
  font-size: 20px;
}
rt {
  color: transparent;
  height: 0px;
  font-size: 30px;
}
span {
  white-space: pre;
}
ruby {
  ruby-overhang: none;
}
</style>
<div>
  <u><ruby><span> </span><rt>annotation</rt></ruby></u>
</div>
<div>
  <u><span> <span><ruby><span> </span><rt>annotation</rt></ruby><span> <span></u>
</div>
<div>
  <span> <span><u><ruby><span> </span><rt>annotation</rt></ruby></u><span> <span>
</div>
<div style="writing-mode: vertical-rl">
  <u><span> <span><ruby><span> </span><rt>annotation</rt></ruby><span> <span></u>
</div>