[Sync] Convert NonBlockingDataTypeController to be single-thread.

components/sync/driver/ui_model_type_controller_unittest.cc

Index: components/sync/driver/ui_model_type_controller_unittest.cc
diff --git a/components/sync/driver/ui_model_type_controller_unittest.cc b/components/sync/driver/ui_model_type_controller_unittest.cc
index 80d66104e7a1e0f5699e64f171ea0bb37f9018fb..081674c8d2a545e16acd0050972d45ff640d09ee 100644
--- a/components/sync/driver/ui_model_type_controller_unittest.cc
+++ b/components/sync/driver/ui_model_type_controller_unittest.cc
@@ -153,9 +153,9 @@ class UIModelTypeControllerTest : public testing::Test,
     RunAllTasks();
   }
 
-  syncer_v2::ModelTypeService* GetModelTypeServiceForType(
+  base::WeakPtr<syncer_v2::ModelTypeService> GetModelTypeServiceForType(
       syncer::ModelType type) override {
-    return service_.get();
+    return service_->AsWeakPtr();
   }
 
  protected: