message: Define missing 'padchar' constant.
diff: var WHITESPACE_REGEX = /\s*/g;
  /** Base64 validation regular expression. */
  var BASE64_PATTERN = new RegExp('^([A-Za-z0-9+/_-]{4})*([A-Za-z0-9+/_-]{4}|[A-Za-z0-9+/_-]{3}=|[A-Za-z0-9+/_-]{2}==)?$');
  + /** Padding character. */
  + var PADCHAR = "=";
  /**
  * <p>Validates that a string is a valid Base64 encoding. This uses a
  if (overhang) {
  var toPad = 4 - overhang;
  for (var i = 0; i < toPad; ++i)
  - sanitized += padchar;
  + sanitized += PADCHAR;
  }
  }
  