JFileChooser filepanel background color is unlike native mercury filedialog file panel background.

The background color of the area having list items is different than background color of the list part without items.
For instance if there are 3 items in the file list, than background color of these 3 items is different than the remaining list background color. This is unlike native where background color is same for both.


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 notice the background color of folder and file list.
4) Now open Gedit.
5) Click Open and notice the background color of folder and file list.
It is same through out the list, It is different than java implementation of the same.