[Sync] Make directory types registration explicit in ModelTypeRegistry

components/sync/driver/glue/sync_backend_host_core.h

Index: components/sync/driver/glue/sync_backend_host_core.h
diff --git a/components/sync/driver/glue/sync_backend_host_core.h b/components/sync/driver/glue/sync_backend_host_core.h
index 787a1eb33781ebec8b4b75936905a1c7f5e15c21..c46814bcf591346e911f164f4eb4de64a34b2c77 100644
--- a/components/sync/driver/glue/sync_backend_host_core.h
+++ b/components/sync/driver/glue/sync_backend_host_core.h
@@ -106,10 +106,14 @@ class SyncBackendHostCore
   // SyncEngine::UpdateCredentials.
   void DoUpdateCredentials(const SyncCredentials& credentials);
 
+  // Switches sync engine into configuration mode. In this mode only initial
+  // data for newly enabled types is downloaded from server. No local changes
+  // are committed to server.
+  void DoStartConfiguration();
+
   // Called to tell the syncapi to start syncing (generally after
   // initialization and authentication).
-  void DoStartSyncing(const ModelSafeRoutingInfo& routing_info,
-                      base::Time last_poll_time);
+  void DoStartSyncing(base::Time last_poll_time);
 
   // Called to set the passphrase for encryption.
   void DoSetEncryptionPassphrase(const std::string& passphrase,