private function send_common_files($oldctxid, $newctxid, $progress) {
        // Add common question files (question and question_answer ones).
        restore_dbops::send_files_to_pool($this->get_basepath(), $this->get_restoreid(), 'question', 'questiontext',
                $oldctxid, $this->task->get_userid(), 'question_created', null, $newctxid, true, $progress);
        restore_dbops::send_files_to_pool($this->get_basepath(), $this->get_restoreid(), 'question', 'generalfeedback',
                $oldctxid, $this->task->get_userid(), 'question_created', null, $newctxid, true, $progress);
        restore_dbops::send_files_to_pool($this->get_basepath(), $this->get_restoreid(), 'question', 'answer',
                $oldctxid, $this->task->get_userid(), 'question_answer', null, $newctxid, true, $progress);
        restore_dbops::send_files_to_pool($this->get_basepath(), $this->get_restoreid(), 'question', 'answerfeedback',
                $oldctxid, $this->task->get_userid(), 'question_answer', null, $newctxid, true, $progress);
        restore_dbops::send_files_to_pool($this->get_basepath(), $this->get_restoreid(), 'question', 'hint',
                $oldctxid, $this->task->get_userid(), 'question_hint', null, $newctxid, true, $progress);
        restore_dbops::send_files_to_pool($this->get_basepath(), $this->get_restoreid(), 'question', 'correctfeedback',
                $oldctxid, $this->task->get_userid(), 'question_created', null, $newctxid, true, $progress);
        restore_dbops::send_files_to_pool($this->get_basepath(), $this->get_restoreid(), 'question', 'partiallycorrectfeedback',
                $oldctxid, $this->task->get_userid(), 'question_created', null, $newctxid, true, $progress);
        restore_dbops::send_files_to_pool($this->get_basepath(), $this->get_restoreid(), 'question', 'incorrectfeedback',
                $oldctxid, $this->task->get_userid(), 'question_created', null, $newctxid, true, $progress);
    }