Move ProfileSyncService::SyncEvent out of ProfileSyncService

and into sync_service_utils.h/cc.
It was already a static function, so easy to move.
Generally, clients should not use (or even have to know about) the
concrete *Profile*SyncService. This also cleans up its interface a bit.

TBRing simple call site updates:
tangltom for profile_chooser_view.cc
dpapad for people_handler.cc
TBR=tangltom,dpapad

Bug: 884159
Change-Id: Id32e943a083d3cb851766171a3d1cfb3f9282ee4
Reviewed-on: https://chromium-review.googlesource.com/c/1367604
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614686}
6 files changed