[Sync] Introduce ModelError for USS error handling.

components/sync/model/fake_model_type_change_processor.h

Index: components/sync/model/fake_model_type_change_processor.h
diff --git a/components/sync/model/fake_model_type_change_processor.h b/components/sync/model/fake_model_type_change_processor.h
index bee92efbfecc1bdb5910be15e4f17278abb414be..5b39a83fb63815092d4b905e4a704145a1d405df 100644
--- a/components/sync/model/fake_model_type_change_processor.h
+++ b/components/sync/model/fake_model_type_change_processor.h
@@ -38,8 +38,11 @@ class FakeModelTypeChangeProcessor : public ModelTypeChangeProcessor {
                       const StartCallback& callback) override;
   void DisableSync() override;
   bool IsTrackingMetadata() override;
+  void OnUnrecoverableError(const SyncError& error) override;
   SyncError CreateAndUploadError(const tracked_objects::Location& location,
-                                 const std::string& message) override;
+                                 const std::string& message,
+                                 ModelType type) override;
+  std::unique_ptr<DataTypeErrorHandler> Copy() const override;
 };
 
 }  // namespace syncer