code: function getCarouselItemSize(which) {
          var carousel = this,
              child,
              item,
              size     = 0,
              first = carousel.get("firstVisible"),
              vertical = false;
  
          if (carousel._itemsTable.numItems === 0) {
              return 0;
          }
  
          item = carousel._itemsTable.items[first] ||
                 carousel._itemsTable.loading[first];
  
          if (JS.isUndefined(item)) {
              return 0;
          }
  
          child = Dom.get(item.id);
  
          if (typeof which == "undefined") {
              vertical = carousel.get("isVertical");
          } else {
              vertical = which == "height";
          }
  
          if (this._itemAttrCache[which]) {
              return this._itemAttrCache[which];
          }
  
          if (vertical) {
              size = getStyle(child, "height");
          } else {
              size = getStyle(child, "width");
          }
  
          this._itemAttrCache[which] = size;
  
          return size;
      }
docs: Compute and return the height or width of a single Carousel item
  depending upon the orientation.
  
  @method getCarouselItemSize
  @param which {String} "height" or "width" to be returned.  If this is
  passed explicitly, the calculated size is not cached.
  @private