We need to use the writing mode of the containing block to do this, not that of
the child, which is completely irrelevant.

Change-Id: Ia5907d9ce60d00ad453f48fb72193e2eab1aaa3e
Reviewed-on: https://chromium-review.googlesource.com/1127047
Reviewed-by: Koji Ishii <[email protected]>
Commit-Queue: Morten Stenshorne <[email protected]>
Cr-Commit-Position: refs/heads/master@{#572931}