R=bradnelson@chromium.org

Bug: chromium:810973
Change-Id: I818c17ef03b27df72976048b1873fc3f3a368900
Reviewed-on: https://chromium-review.googlesource.com/914330Reviewed-by: Brad Nelson <bradnelson@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51252}