@Nullable
  private static AirContentRevision convertRevision(@Nullable ContentRevision cr, @Nullable String actualTextContent) {
    if (cr == null) {
      return null;
    }

    FilePath filePath = cr.getFile();
    if (actualTextContent != null) {
      return new PartialTextAirContentRevision(actualTextContent, cr, filePath);
    }
    else if (cr instanceof ByteBackedContentRevision &&
             isBinaryRevision(cr)) {
      return new BinaryAirContentRevision((ByteBackedContentRevision)cr, filePath);
    }
    else {
      return new TextAirContentRevision(cr, filePath);
    }
  }
@Nullable
  private static AirContentRevision convertRevision(@Nullable ContentRevision cr, @Nullable String actualTextContent)