Grid grid = new Grid();
grid.addColumn("a");//add a column, but not add data
grid.setHeightMode(HeightMode.ROW);
grid.setHeightByRows(1);//the height is not exactly row height
when grid have some data, The height of a row is 38px,
but when grid no data, The height of a row smaill than 38px. it seem like 20px
and i can not use the method setHeight, so i can not control the height of my grid when grid init.