code: private void addFacetNameToParentTag(UIComponentClassicTagBase parentTag, String facetName)
      {
          if (parentTag._facetsAdded == null)
          {
              parentTag._facetsAdded = new ArrayList<String>();
          }
          parentTag._facetsAdded.add(facetName);
      }
docs: Notify the enclosing JSP tag of the id of this facet's id. The parent tag will later delete any existing view
  facets that were not seen during this rendering phase; see doEndTag for details.