GitLab

MessagePumpType is used in other places (eg base/thread.h). Moving it to
its own file will simplify include dependencies.

Bug: 891670
Change-Id: I214342da0d6833e0ad324cd4d58c08a0233f7c1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1718806
Commit-Queue: Carlos Caballero <carlscab@google.com>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682235}