LayoutTests/fast/ruby/ruby-in-vertical-writing-mode-with-long-annotation.html

<style>
.container {
  background-color: green;
  color: transparent;
  writing-mode: vertical-lr;
  font-family: Ahem;
  font-size: 10px;
}
rt {
  font-size: 10px;
}
</style>
<div class=container><ruby>PASS<br>if<rt>annotation does not stretch the box horizontally</rt></ruby></div>