[Sync] Introduce ModelError for USS error handling.

components/sync/model/fake_model_type_change_processor.cc

Index: components/sync/model/fake_model_type_change_processor.cc
diff --git a/components/sync/model/fake_model_type_change_processor.cc b/components/sync/model/fake_model_type_change_processor.cc
index e0df9d869a1ac6237a1a68b1f3e3a297102d2a54..5102b8106d78910059f93735bf388cf66a8f8b34 100644
--- a/components/sync/model/fake_model_type_change_processor.cc
+++ b/components/sync/model/fake_model_type_change_processor.cc
@@ -49,10 +49,20 @@ bool FakeModelTypeChangeProcessor::IsTrackingMetadata() {
   return true;
 }
 
+void FakeModelTypeChangeProcessor::OnUnrecoverableError(
+    const SyncError& error) {}
+
 SyncError FakeModelTypeChangeProcessor::CreateAndUploadError(
     const tracked_objects::Location& location,
-    const std::string& message) {
+    const std::string& message,
+    ModelType type) {
   return SyncError();
 }
 
+std::unique_ptr<DataTypeErrorHandler> FakeModelTypeChangeProcessor::Copy()
+    const {
+  NOTREACHED();
+  return nullptr;
+}
+
 }  // namespace syncer