//Add data
for (var col = 1; col < 6; col++) {
    for (var row = 2; row < 11; row++) {
        activeSheet.setValue(row, col, row + col);
    }
}
activeSheet.setRowHeight(3, 90.0,GC.Spread.Sheets.SheetArea.viewport);

$("#button1").click(function () {
spread.options.allowUndo = true;
var rows = [ { row: 3 } ];
spread.commandManager().execute({cmd: "autoFitRow", sheetName: "Sheet1", rows: rows, isColHeader: false, autoFitType: GC.Spread.Sheets.AutoFitType.cell});
    });

<input type="button" id="button1" value="button1"/>