Remove SyncService::RequestStart

It has been replaced by SyncUserSettings::SetSyncRequested(true).
Note that *Profile*SyncService::RequestStart still exists for now
(it's used by SyncUserSettings). This will be changed in a later CL.

Bug: 884159
Change-Id: Ie96e6a999ae6060fd3bbe444e4471ba9327edef8
Reviewed-on: https://chromium-review.googlesource.com/c/1350907
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611609}
7 files changed