R=clemensh@chromium.org
BUG=chromium:789952

Change-Id: Ida627fa6cdeacff01a0ec4d20e58281f17528010
Reviewed-on: https://chromium-review.googlesource.com/800941Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49767}