constructor(callback, opt_hideTitle, opt_actionBtnTitle) {
    super();

    /**
     * The callback to invoke when a new PGP key is to be generated.
     * @type {!function(...)}
     * @private
     */
    this.callback_ = callback;

    /**
     * The title for the generate key section. If empty, it will not be
     * displayed.
     * @type {string}
     * @private
     */
    this.sectionTitle_ =
        Boolean(opt_hideTitle) ? '' : chrome.i18n.getMessage('genKeyTitle');

    /**
     * The title for the action button.
     * @type {string}
     * @private
     */
    this.actionButtonTitle_ = opt_actionBtnTitle ||
        chrome.i18n.getMessage('genKeyGenerateButtonLabel');
  }
@param {!function(...)} callback The callback to invoke when a new PGP key
    is to be generated.
@param {boolean=} opt_hideTitle Optional. A flag to control the display of
    the section title. If true, the section title will not be displayed.
    Defaults to false.
@param {string=} opt_actionBtnTitle Optional. The title for the action
    button. Uses extension defaults if not specified.