function enqueueSetMarkup(parentID, markup) {
  // NOTE: Null values reduce hidden classes.
  updateQueue.push({
    parentID: parentID,
    parentNode: null,
    type: ReactMultiChildUpdateTypes.SET_MARKUP,
    markupIndex: null,
    content: markup,
    fromIndex: null,
    toIndex: null
  });
}
Enqueues setting the markup of a node.

@param {string} parentID ID of the parent component.
@param {string} markup Markup that renders into an element.
@private