JScrollbar policy in JFileChooser is unlike native mercury file dialog policy. In native vertical scrollbars are always present i.e there presence is independent of list item count or size of file dialog whereas in Java implementation scrollbars appears only if they are needed i.e. VERTICAL_SCROLLBAR_AS_NEEDED.

Steps to Reproduce:
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1) Run SwingSet2 on Mercury with -Dswing.gtkthemefile=<Your .gtkrc File>. Change the Look And Feel to GTK.
2) Go to FileChooser Demo.
3) Click on button 'Show Plain JFileChooser' and resize(reduce) it till you get vertical scrollbar, Now increase the size of file dialog by resizing again and notice the vertical scrollbars will disappear.
4) Now open Gedit.
5) Click Open and try resizing it by reducing size or increasing size, Scrollbar will never go. It is different than java implementation of the same.