Set a border around editor without affecting inner component. Basically an overlay instead.

I am using below: 

protected void onFocus(EditorImpl focused) {
        focused.getScrollPane().setBorder(BORDER);
}

But if border adds top, bottom, left, right. Then the inner editor is resizing. I want a marker for the editor without affecting the border.

In HTML this would be achived by resizing the innercomponent so that eveything remaing the same size. 

Not sure how to achieve that here.