code: function replaceWithPlainText(selector, regex) {
    return selector.replace(regex, function(match) {
      return Array(match.length + 1).join('A');
    });
  }
docs: Replace escaped characters with plain text, using the "A" character.
  @see https://www.w3.org/TR/CSS21/syndata.html#characters
  @param {string} selector
  @param {!RegExp} regex
  @return {string}