phorge-phorge/src/applications/files/storage/PhabricatorFileTransactionComment.php

<?php

final class PhabricatorFileTransactionComment
  extends PhabricatorApplicationTransactionComment {

  public function getApplicationTransactionObject() {
    return new PhabricatorFileTransaction();
  }

  public function shouldUseMarkupCache($field) {
    // Only cache submitted comments.
    return ($this->getTransactionPHID() != null);
  }

}