GitLab

Aimed to avoid ref-counted lifecycle of TaskQueueImpl.
SingleThreadTaskRunnner implementation will be dropped
from TaskQueue shortly. See bug for details.

TBR=gab@chromium.org

Bug: 865411
Change-Id: I92a3965299cb1c829e8a385f4bb2690383436107
Reviewed-on: https://chromium-review.googlesource.com/1234474
Commit-Queue: Greg Kraynov <kraynov@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593185}