Method build

src/custom-element.js:611–626

* @return {!Promise}

()

     * @return {!Promise}
     */
    build() {
      if (this.buildingPromise_) {
        return this.buildingPromise_;
      }

      const readyPromise = this.signals_.whenSignal(
        CommonSignals_Enum.READY_TO_UPGRADE
      );
      return readyPromise.then(() => {
        if (this.R1()) {
          const scheduler = getSchedulerForDoc(this.getAmpDoc());
          scheduler.scheduleAsap(this);
        }
        return this.whenBuilt();
      });
    }

    /**
     * Mounts the element by calling the `BaseElement.mountCallback` method.