Sync for secondary accounts: No Sync confirmation needed

ProfileSyncService::IsSyncConfirmationNeeded is used by the UI as a signal
for showing a Sync error (see
AvatarButtonErrorController::SyncErrorObserver::HasSyncError). This is not
appropriate if Sync is running in transport-only mode for a secondary
account (there's nothing to confirm). So this CL changes
IsSyncConfirmationNeeded to return false if the current account isn't
primary. This fixes a wrongly-shown "Sync error" in the avatar button.

Bug: 871221
Change-Id: Icdaa5f7b46acd6eac1a65adc4d49d20296a6f044
Reviewed-on: https://chromium-review.googlesource.com/1196364Reviewed-by: Jan Krcal <jkrcal@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587547}

components/browser_sync/profile_sync_service.cc

@@ -891,7 +891,8 @@ bool ProfileSyncService::IsSyncConfirmationNeeded() const {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   return (!IsLocalSyncEnabled() && IsSignedIn()) && !IsSetupInProgress() &&
          !IsFirstSetupComplete() &&
-         !HasDisableReason(DISABLE_REASON_USER_CHOICE);
+         !HasDisableReason(DISABLE_REASON_USER_CHOICE) &&
+         IsAuthenticatedAccountPrimary();
 }
 
 void ProfileSyncService::UpdateLastSyncedTime() {