Method whenMounted

src/custom-element.js:771–773

* Returns the promise that's resolved when the element has been mounted. If * the mount fails, the resulting promise is rejected. * @return {!Promise}

()

     * @return {!Promise}
     */
    whenMounted() {
      return this.signals_.whenSignal(CommonSignals_Enum.MOUNTED);
    }

    /**
     * @return {!Promise}