[Sync] Register USS types with ModelTypeRegistry before download

components/sync_driver/fake_data_type_controller.cc

Index: components/sync_driver/fake_data_type_controller.cc
diff --git a/components/sync_driver/fake_data_type_controller.cc b/components/sync_driver/fake_data_type_controller.cc
index a0c290eea4f814c2682eadb9dd91abbc4bdb3b0e..e8bf1c1084927450922112152ac3098a4da37c4d 100644
--- a/components/sync_driver/fake_data_type_controller.cc
+++ b/components/sync_driver/fake_data_type_controller.cc
@@ -20,7 +20,8 @@ FakeDataTypeController::FakeDataTypeController(ModelType type)
       model_load_delayed_(false),
       type_(type),
       ready_for_start_(true),
-      should_load_model_before_configure_(false) {}
+      should_load_model_before_configure_(false),
+      register_with_backend_call_count_(0) {}
 
 FakeDataTypeController::~FakeDataTypeController() {
 }
@@ -49,6 +50,11 @@ void FakeDataTypeController::LoadModels(
   }
 }
 
+void FakeDataTypeController::RegisterWithBackend(
+    BackendDataTypeConfigurer* configurer) {
+  ++register_with_backend_call_count_;
+}
+
 // MODEL_LOADED -> MODEL_STARTING.
 void FakeDataTypeController::StartAssociating(
     const StartCallback& start_callback) {