[Sync] Make directory types registration explicit in ModelTypeRegistry

components/sync/engine/sync_manager.h

Index: components/sync/engine/sync_manager.h
diff --git a/components/sync/engine/sync_manager.h b/components/sync/engine/sync_manager.h
index 37e7de633eca0dd9d13d58b571cc697c6a7378d0..223ced40ddf0cb4e6bfb7bc8ad53834a05dd51a1 100644
--- a/components/sync/engine/sync_manager.h
+++ b/components/sync/engine/sync_manager.h
@@ -304,8 +304,11 @@ class SyncManager {
   virtual void UpdateCredentials(const SyncCredentials& credentials) = 0;
 
   // Put the syncer in normal mode ready to perform nudges and polls.
-  virtual void StartSyncingNormally(const ModelSafeRoutingInfo& routing_info,
-                                    base::Time last_poll_time) = 0;
+  virtual void StartSyncingNormally(base::Time last_poll_time) = 0;
+
+  // Put syncer in configuration mode. Only configuration sync cycles are
+  // performed. No local changes are committed to the server.
+  virtual void StartConfiguration() = 0;
 
   // Switches the mode of operation to CONFIGURATION_MODE and performs
   // any configuration tasks needed as determined by the params. Once complete,
@@ -317,7 +320,6 @@ class SyncManager {
   //              does finish.
   virtual void ConfigureSyncer(ConfigureReason reason,
                                ModelTypeSet to_download,
-                               const ModelSafeRoutingInfo& new_routing_info,
                                const base::Closure& ready_task,
                                const base::Closure& retry_task) = 0;
 
@@ -352,7 +354,8 @@ class SyncManager {
   // May be called from any thread.
   virtual UserShare* GetUserShare() = 0;
 
-  // Returns an instance of the main interface for non-blocking sync types.
+  // Returns an instance of the main interface for registering sync types with
+  // sync engine.
   virtual std::unique_ptr<ModelTypeConnector> GetModelTypeConnectorProxy() = 0;
 
   // Returns the cache_guid of the currently open database.