The following lines of code in policy/common/core/schema.cc:

  storage->schema_data_.schema_nodes = data->schema_nodes;
  storage->schema_data_.property_nodes = data->property_nodes;
  storage->schema_data_.properties_nodes = data->properties_nodes;
  storage->schema_data_.restriction_nodes = data->restriction_nodes;
  storage->schema_data_.required_properties = data->required_properties;
  storage->schema_data_.int_enums = data->int_enums;
  storage->schema_data_.string_enums = data->string_enums;
  storage->schema_data_.validation_schema_root_index =
      data->validation_schema_root_index;

Could probably be replaced by using an auto-generated copy constructor - unless the original author had a reason not to use them.
Will try it out.