Remove SyncService::IsFirstSetupComplete

It has been replaced by SyncUserSettings::IsFirstSetupComplete.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

There were 3 remaining places that still used the SyncService version
of IsFirstSetupComplete; those are trivially migrated to
SyncUserSettings.

Bug: 884159
Change-Id: I90b29436986a7220803c61e2f2767c620e291e71
Reviewed-on: https://chromium-review.googlesource.com/c/1352785
Reviewed-by: Christian Dullweber <dullweber@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612091}
12 files changed