src/common/js/winjs/js/ui.js
function _LayoutCommon_getItemInfo(itemIndex) {
                    var result;
                    if (!this._itemInfo || typeof this._itemInfo !== "function") {
                        if (this._useDefaultItemInfo) {
                            result = this._defaultItemInfo(itemIndex);
                        } else {
                            throw new _ErrorFromName("WinJS.UI.GridLayout.ItemInfoIsInvalid", strings.itemInfoIsInvalid);
                        }
                    } else {
                        result = this._itemInfo(itemIndex);
                    }
                    return Promise.as(result).then(function (size) {
                        if (!size || +size.width !== size.width || +size.height !== size.height) {
                            throw new _ErrorFromName("WinJS.UI.GridLayout.ItemInfoIsInvalid", strings.itemInfoIsInvalid);
                        }
                        return size;
                    });
                }
function _LayoutCommon_getItemInfo(itemIndex) {
                    var result;
                    if (!this._itemInfo || typeof this._itemInfo !== "function") {
                        if (this._useDefaultItemInfo) {
                            result = this._defaultItemInfo(itemIndex);
                        } else {
                            throw new _ErrorFromName("WinJS.UI.GridLayout.ItemInfoIsInvalid", strings.itemInfoIsInvalid);
                        }
                    } else {
                        result = this._itemInfo(itemIndex);
                    }
                    return Promise.as(result).then(function (size) {
                        if (!size || +size.width !== size.width || +size.height !== size.height) {
                            throw new _ErrorFromName("WinJS.UI.GridLayout.ItemInfoIsInvalid", strings.itemInfoIsInvalid);
                        }
                        return size;
                    });
                }
function _LayoutCommon_getItemInfo ( itemIndex ) { var result ; if ( ! this . _itemInfo || typeof this . _itemInfo !== "function" ) { if ( this . _useDefaultItemInfo ) { result = this . _defaultItemInfo ( itemIndex ) ; } else { throw new _ErrorFromName ( "WinJS.UI.GridLayout.ItemInfoIsInvalid" , strings . itemInfoIsInvalid ) ; } } else { result = this . _itemInfo ( itemIndex ) ; } return Promise . as ( result ) . then ( function ( size ) { if ( ! size || + size . width !== size . width || + size . height !== size . height ) { throw new _ErrorFromName ( "WinJS.UI.GridLayout.ItemInfoIsInvalid" , strings . itemInfoIsInvalid ) ; } return size ; } ) ; }
itemIndex is optional
itemIndex is optional