[Sync] Notify observers when IsSyncRequested goes from true to false.

components/browser_sync/browser/profile_sync_service.cc

Index: components/browser_sync/browser/profile_sync_service.cc
diff --git a/components/browser_sync/browser/profile_sync_service.cc b/components/browser_sync/browser/profile_sync_service.cc
index a41b846d748d38185b63c7bdc93751727ff758ed..872f44eb8b51d0db3cb5a484a006b350f7e30b04 100644
--- a/components/browser_sync/browser/profile_sync_service.cc
+++ b/components/browser_sync/browser/profile_sync_service.cc
@@ -2359,8 +2359,10 @@ void ProfileSyncService::RequestStart() {
     return;
   }
   DCHECK(sync_client_);
-  sync_prefs_.SetSyncRequested(true);
-  DCHECK(!signin_.get() || signin_->GetOriginal()->IsAuthenticated());
+  if (!IsSyncRequested()) {
+    sync_prefs_.SetSyncRequested(true);
+    NotifyObservers();
+  }
   startup_controller_->TryStart();
 }