[Sync] Rework Invalidator-related unit tests

sync/notifier/invalidator_registrar.h

Index: sync/notifier/invalidator_registrar.h
diff --git a/sync/notifier/invalidator_registrar.h b/sync/notifier/invalidator_registrar.h
index 6bb481b5f0ae1e63108fb71f80350130cfa727dc..485b73e309238b2f08474f3e7b4acb44cf857388 100644
--- a/sync/notifier/invalidator_registrar.h
+++ b/sync/notifier/invalidator_registrar.h
@@ -44,6 +44,8 @@ class InvalidatorRegistrar {
   // associated with |handler|.
   void UnregisterHandler(InvalidationHandler* handler);
 
+  ObjectIdSet GetRegisteredIds(InvalidationHandler* handler) const;
+
   // Returns the set of all IDs that are registered to some handler (even
   // handlers that have been unregistered).
   ObjectIdSet GetAllRegisteredIds() const;
@@ -60,7 +62,6 @@ class InvalidatorRegistrar {
   void EmitOnNotificationsDisabled(NotificationsDisabledReason reason);
 
   bool IsHandlerRegisteredForTest(InvalidationHandler* handler) const;
-  ObjectIdSet GetRegisteredIdsForTest(InvalidationHandler* handler) const;
 
   // Needed for death tests.
   void DetachFromThreadForTest();