<!DOCTYPE html>
<title>Two levels of writing mode roots with text inside, percentage inline size on inner</title>
<link rel="author" title="Morten Stenshorne" href="mstensho@chromium.org">
<p>There should be three lines below. The middle line should have a yellow
  background that takes up about 50% of the viewport width (but otherwise be
  exactly like the two others, i.e. no extra height or anything like that).</p>
A B C D E F G
<div style="width:50vw; background:yellow;">
  A B C D E F G
</div>
A B C D E F G