The classes BasicFileChooserUI, MetalFileChooserUI, and WindowsFileChooserUI
are very big and contain a large amount of common or similar code. By extracting
the code that handles the scrolling list/table of files into a separate
shared class, this code would become much easier to maintain and would
allow for more reliable bug fixes and enhancements in the future.

###@###.### 2003-05-09