Provide the same sidebar items in a native and non-native file dialog on the Mac

The sidebar of a native Mac file dialog shows each volume followed by "$HOME" and some other common directories. Providing the same sidebar items in a native and non-native file dialog will provide a more consistent and less confusing user experience. Currently the sidebar in a non-native Mac filedialog only shows "Computer" and "$HOME." The additional volumes are not shown and therefore it is not possible to select files from them.