R=clemensh@chromium.org

Bug: chromium:766003,chromium:772332,chromium:771243
Change-Id: I1e2df014f31a87fd94154277d1a415ec359d42df
Reviewed-on: https://chromium-review.googlesource.com/721666Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48635}