[Sync] Create UserEventSyncBridge.

components/sync/model/model_type_store_test_util.h

Index: components/sync/model/model_type_store_test_util.h
diff --git a/components/sync/model/model_type_store_test_util.h b/components/sync/model/model_type_store_test_util.h
index 8bcf4bcc47c11e1f323edca3c0472529dc4096d3..e911f46c039af9f3dea1fb36763851f32f339165 100644
--- a/components/sync/model/model_type_store_test_util.h
+++ b/components/sync/model/model_type_store_test_util.h
@@ -15,10 +15,13 @@ namespace syncer {
 // classes that use ModelTypeStore objects.
 class ModelTypeStoreTestUtil {
  public:
-  // Creates an in memory store syncronously. Be aware that to do this all
+  // Creates an in memory store synchronously. Be aware that to do this all
   // outstanding tasks will be run as the current message loop is pumped.
   static std::unique_ptr<ModelTypeStore> CreateInMemoryStoreForTest();
 
+  // Creates a factory callback to synchronously return an in memory store.
+  static ModelTypeStoreFactory FactoryForInMemoryStoreForTest();
+
   // Can be curried with an owned store object to allow passing an already
   // created store to a service constructor in a unit test.
   static void MoveStoreToCallback(std::unique_ptr<ModelTypeStore> store,