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These were previously only exposed in *Profile*SyncService. Moving them
up into the interface removes one of the last reasons to use
ProfileSyncService directly.

Bug: 924508
Change-Id: Ie7f44f4dc8adba814812b9fae9bf3e753c7890c5
Reviewed-on: https://chromium-review.googlesource.com/c/1458038Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629967}