[Sync] Let ModelTypeRegistry filter out initial download USS types.

components/sync/engine_impl/model_type_registry.h

Index: components/sync/engine_impl/model_type_registry.h
diff --git a/components/sync/engine_impl/model_type_registry.h b/components/sync/engine_impl/model_type_registry.h
index f6cf21d2cc50205bb5e46f12bd16c82e3a508614..f238513b1e6ad0ab8f6e2b955b3d067d49aad58b 100644
--- a/components/sync/engine_impl/model_type_registry.h
+++ b/components/sync/engine_impl/model_type_registry.h
@@ -87,6 +87,9 @@ class ModelTypeRegistry : public ModelTypeConnector,
   // applied.
   ModelTypeSet GetInitialSyncEndedTypes() const;
 
+  // Returns the set of non-blocking types with initial sync done.
+  ModelTypeSet GetInitialSyncDoneNonBlockingTypes() const;
+
   // Simple getters.
   UpdateHandlerMap* update_handler_map();
   CommitContributorMap* commit_contributor_map();