Introduce GoogleUpdateSettings::CollectStatsConsentTaskRunner and get rid of FILE thread usage in callers.

An Android caller was also using BlockingPool() to make this call before
so this was potentially racy there.

R=asviktine@chromium.org, grt@chromium.org

Bug: 730170, 667892, 689520
Change-Id: I04aacb46379f4e6e6fc27df5ddf09b05a860e223
Reviewed-on: https://chromium-review.googlesource.com/543560
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#484389}
7 files changed