[Sync] InvalidationService shouldn't CHECK when registering ObjectId for more than one handler

components/invalidation/invalidator_registrar.h

Index: components/invalidation/invalidator_registrar.h
diff --git a/components/invalidation/invalidator_registrar.h b/components/invalidation/invalidator_registrar.h
index e6804bbfb14a82dd22363bc8b54e95215a0f11c8..d0ab22dbafe0435001ca044367b23981354bfc0f 100644
--- a/components/invalidation/invalidator_registrar.h
+++ b/components/invalidation/invalidator_registrar.h
@@ -39,9 +39,9 @@ class INVALIDATION_EXPORT InvalidatorRegistrar {
 
   // Updates the set of ObjectIds associated with |handler|.  |handler| must
   // not be NULL, and must already be registered.  An ID must be registered for
-  // at most one handler.
-  void UpdateRegisteredIds(InvalidationHandler* handler,
-                           const ObjectIdSet& ids);
+  // at most one handler. If ID is already registered function returns false.
+  bool UpdateRegisteredIds(InvalidationHandler* handler,
+                           const ObjectIdSet& ids) WARN_UNUSED_RESULT;
 
   // Stops sending notifications to |handler|.  |handler| must not be NULL, and
   // it must already be registered.  Note that this doesn't unregister the IDs