Introduce SyncService::RequiresClientUpgrade

Currently, a bunch of places call QueryDetailedSyncStatus() (a fairly
low-level for-debugging method) to detect specifically whether the
Chrome client is too old and needs to be updated for Sync to work.
This CL adds a new SyncService API that exposes this bit specifically,
and updates sync_ui_util to use it.
As a follow-up, we can mark QueryDetailedSyncStatus as "ForDebugging".

Bug: 940437
Change-Id: I30a30a66366f4d3bb52e465bdfd4130003c943d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1523095
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641632}
10 files changed