Unable to see scrollbar in TextAreaItem control

GWT 2.4.0, Browser ie8,
sample code{

TextArea txt=new TextArea()
TextAreaItem item = new TextAreaItem(name, label);
item.setWrapTitle(true);
item.setRequired(true);
item.setWidth(600);
item.setHeight(50);
item.setTextBoxStyle("overflow-auto");
return item;}

CSS used ,

.overflow-auto {
overflow: auto;
}

still there is no scrollbar at all

Please help
Saurabh jain