GtkFileChooserButton widget which uses dialog as its
file-picking window.gtkFileChooserButtonNewWithDialog(dialog)dialogGtkWidget] a new button widget.dialog must be a GtkDialog (or subclass) which
implements the GtkFileChooser interface and must not have
GTK_DIALOG_DESTROY_WITH_PARENT set.
Also note that the dialog needs to have its confirmative button
added with response GTK_RESPONSE_ACCEPT or GTK_RESPONSE_OK in
order for the button to take over the file selected in the dialog.
Since 2.6