code: function _stripStartingSlashIfNeeded(file_path) {
      if (file_path.substring(0, 1) !== '/') {
        return file_path;
      }
      if (pathUtils.exists(file_path))
        return file_path;
      return file_path.substring(1);
    }
docs: Strips the starting '/' in file_path if |file_path| is meant to be a
  relative path.
  
  @param {string} file_path path to some file, can be relative or absolute
  path.
  @return {string} the file_path with starting '/' removed if |file_path|
  does not exist or the original |file_path| otherwise.