constructor(api) {
    super();

    /**
     * The handler to get the value of the selected element.
     * @type {function(...)}
     * @private
     */
    this.boundMessageHandler_ = goog.bind(this.handleMessage_, this);

    /**
     * @type {!e2e.ext.WebsiteApi} Website API connector instance to send
     *     queries through.
     * @private
     */
    this.api_ = api;

    chrome.runtime.onMessage.addListener(this.boundMessageHandler_);
  }
@param {!e2e.ext.WebsiteApi} api Website API connector instance to use