docs: function enqueueMarkup(parentID, markup, toIndex) {
    // NOTE: Null values reduce hidden classes.
    updateQueue.push({
      parentID: parentID,
      parentNode: null,
      type: ReactMultiChildUpdateTypes.INSERT_MARKUP,
      markupIndex: markupQueue.push(markup) - 1,
      textContent: null,
      fromIndex: null,
      toIndex: toIndex
    });
  }