function removeExportAnnotationsFromComment(comment) {
  // Remove @export annotations.
  comment = comment.replace(EXPORT_REGEX, '');

  // Split into lines, remove empty comment lines, then recombine.
  comment = comment.split('\n')
      .filter((line) => !/^ *\*? *$/.test(line))
      .join('\n');

  return comment;
}
Take the original block comment and prep it for the externs by removing
export annotations and blank lines.

@param {string} comment
@return {string}