[Sync] When a data type is not initialized, also should not be registered with backend.

components/sync/driver/data_type_manager_impl.h

Index: components/sync/driver/data_type_manager_impl.h
diff --git a/components/sync/driver/data_type_manager_impl.h b/components/sync/driver/data_type_manager_impl.h
index 27d9da4418d5ae75f042b66dfda576c2a1dfcd51..571590874f3241885e705e176583e65d55e0bca1 100644
--- a/components/sync/driver/data_type_manager_impl.h
+++ b/components/sync/driver/data_type_manager_impl.h
@@ -145,6 +145,9 @@ class DataTypeManagerImpl : public DataTypeManager,
 
   void StopImpl();
 
+  // Returns the currently enabled types.
+  syncer::ModelTypeSet GetEnabledTypes() const;
+
   BackendDataTypeConfigurer* configurer_;
   // Map of all data type controllers that are available for sync.
   // This list is determined at startup by various command line flags.
@@ -152,6 +155,10 @@ class DataTypeManagerImpl : public DataTypeManager,
   State state_;
   syncer::ModelTypeSet last_requested_types_;
 
+  // A set of types that were enabled at the time initialization with the
+  // |model_association_manager_| was last attempted.
+  syncer::ModelTypeSet last_enabled_types_;
+
   // Whether an attempt to reconfigure was made while we were busy configuring.
   // The |last_requested_types_| will reflect the newest set of requested types.
   bool needs_reconfigure_;