Method whenFirstVisible

src/service/ampdoc-impl.js:684–688

* Returns a Promise that only ever resolved when the current * AMP document first becomes visible. * @return {!Promise}

()

   * @return {!Promise}
   */
  whenFirstVisible() {
    return this.signals_
      .whenSignal(AmpDocSignals_Enum.FIRST_VISIBLE)
      .then(() => undefined);
  }

  /**
   * Returns a Promise that resolve when current doc becomes visible.