R=petermarshall@chromium.org

Bug: 
Change-Id: Id7187d9e323951e66655d1c6df4676a8e94787dd
Reviewed-on: https://chromium-review.googlesource.com/649247Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47815}