[Sync] USS: Fix race condition in DeviceInfoService + add error handling

sync/api/fake_model_type_change_processor.cc

Index: sync/api/fake_model_type_change_processor.cc
diff --git a/sync/api/fake_model_type_change_processor.cc b/sync/api/fake_model_type_change_processor.cc
index bb4775207a7c8b2332533d8d43ae5405d73f87d2..c8932e23880cc23bcae201e2647df9a940b883c5 100644
--- a/sync/api/fake_model_type_change_processor.cc
+++ b/sync/api/fake_model_type_change_processor.cc
@@ -49,4 +49,10 @@ void FakeModelTypeChangeProcessor::OnSyncStarting(
 
 void FakeModelTypeChangeProcessor::DisableSync() {}
 
+syncer::SyncError FakeModelTypeChangeProcessor::CreateAndUploadError(
+    const tracked_objects::Location& location,
+    const std::string& message) {
+  return syncer::SyncError();
+}
+
 }  // namespace syncer_v2