GitLab

Moves IO thread-specific initialization into WebSubThread.

BUG=826465

Change-Id: I5527dafdf75c29fbc8478f7500c20a96410ad008
Reviewed-on: https://chromium-review.googlesource.com/c/1335961Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608898}