USS SyncContextProxy / data type activation refactoring

components/sync_driver/ui_data_type_controller.h

Index: components/sync_driver/ui_data_type_controller.h
diff --git a/components/sync_driver/ui_data_type_controller.h b/components/sync_driver/ui_data_type_controller.h
index 9ebc6a37d30e01b02ef1162c5760ada315f9fdc8..f935f540e834e14cd88b22f645688504b9f3c8e3 100644
--- a/components/sync_driver/ui_data_type_controller.h
+++ b/components/sync_driver/ui_data_type_controller.h
@@ -75,9 +75,6 @@ class UIDataTypeController : public DirectoryDataTypeController {
   // the datatype controller. The default implementation is a no-op.
   virtual void StopModels();
 
-  // DataTypeController interface.
-  void OnModelLoaded() override;
-
   // Helper method for cleaning up state and invoking the start callback.
   virtual void StartDone(ConfigureResult result,
                          const syncer::SyncMergeResult& local_merge_result,
@@ -88,6 +85,11 @@ class UIDataTypeController : public DirectoryDataTypeController {
   // Record causes of start failure.
   virtual void RecordStartFailure(ConfigureResult result);
 
+  // If the DTC is waiting for models to load, once the models are
+  // loaded the datatype service will call this function on DTC to let
+  // us know that it is safe to start associating.
+  void OnModelLoaded();
+
   SyncClient* const sync_client_;
 
   State state_;