code: function acceptSlide(priv, slideElement) {
    slideElement.classList.add(Flag.UPGRADED);
    insertSlide(priv, slideElement);
  
    priv.phaser.addPhaseTrigger(slideElement.querySelector('.'+ Layout.CONTENT));
  
    if (priv.slides.length === 1) {
      priv.startCallback.call(null, priv.pub);
      // moving this to next tick is required in chromium for some reason
      window.setTimeout(moveToFirstSlide.bind(null, priv), 1);
    }
  }
docs: private initialization functions