code: function _LayoutCommon_ensureContainerSize(group) {
                      var sizes = this._sizes;
                      if (!sizes.containerSizeLoaded && !this._ensuringContainerSize) {
                          var promise;
                          if ((!this._itemInfo || typeof this._itemInfo !== "function") && this._useDefaultItemInfo) {
                              var margins = sizes.containerMargins;
                              promise = Promise.wrap({
                                  width: group.groupInfo.cellWidth - margins.left - margins.right,
                                  height: group.groupInfo.cellHeight - margins.top - margins.bottom
                              });
  
                          } else {
                              promise = this._getItemInfo();
                          }
  
                          var that = this;
                          this._ensuringContainerSize = promise.then(function (itemSize) {
                              sizes.containerSizeLoaded = true;
                              sizes.containerWidth = itemSize.width + sizes.itemBoxOuterWidth + sizes.containerOuterWidth;
                              sizes.containerHeight = itemSize.height + sizes.itemBoxOuterHeight + sizes.containerOuterHeight;
                              if (!that._inListMode) {
                                  that._itemsPerBar = Math.floor(sizes.maxItemsContainerContentSize / sizes.containerCrossSize);
                                  if (that.maximumRowsOrColumns) {
                                      that._itemsPerBar = Math.min(that._itemsPerBar, that.maximumRowsOrColumns);
                                  }
                                  that._itemsPerBar = Math.max(1, that._itemsPerBar);
                              } else {
                                  that._itemsPerBar = 1;
                              }
                              that._createContainerStyleRule();
                          });
  
                          promise.done(
                              function () {
                                  that._ensuringContainerSize = null;
                              },
                              function () {
                                  that._ensuringContainerSize = null;
                              }
                          );
  
                          return promise;
                      } else {
                          return this._ensuringContainerSize ? this._ensuringContainerSize : Promise.wrap();
                      }
                  }
docs: Computes container width and height if they haven't been computed yet. This should happen when the first uniform group is created.