GitLab

We are no longer considering having anything other than a FIFO
scheduler on the IO thread (which is why it was added in the
first place).

Split off from https://crrev.com/c/1320329.

TBR=gab@chromium.org

Bug: 863341, 891670
Change-Id: I6e7c4fdd2772ec85dfffcf4bad051b0785b0a050
Reviewed-on: https://chromium-review.googlesource.com/c/1335930
Commit-Queue: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Alex Clarke <alexclarke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608008}