selectCookie(cookieKey) {
    'use strict';
    goog.asserts.assert(goog.net.Cookies.getInstance().isValidName(cookieKey));
    this.cookieKey_ = cookieKey;
    if (this.textAreaElem_) {
      this.textAreaElem_.value =
          goog.net.Cookies.getInstance().get(cookieKey) || '';
    }
  }
Sets the cookie which this component will edit.
@param {string} cookieKey Cookie key.