getInputValue_() {
    var inputs = goog.array.toArray(
        goog.dom.getElementsByClass('keyring-restore-input'));
    return inputs.reduce(function(a, e) {
      return a + e.value;
    }, '');
  }
Parses the user input into a base64 encoded string.
@private
@return {string} The base 64 encoded backup code.