6987233: FileDialog.getDirectory() should add a trainling slash when GTK FileDialog is used

Summary: Add the trailing slash if it's absent
Reviewed-by: art, dcherepanov

jdk/src/solaris/classes/sun/awt/X11/GtkFileDialogPeer.java

@@ -64,7 +64,10 @@ class GtkFileDialogPeer extends XDialogPeer implements FileDialogPeer {
             accessor.setFile(fd, null);
             accessor.setFiles(fd, null, null);
         } else {
-            accessor.setDirectory(fd, directory);
+            // Fix 6987233: add the trailing slash if it's absent
+            accessor.setDirectory(fd, directory +
+                    (directory.endsWith(File.separator) ?
+                     "" : File.separator));
             accessor.setFile(fd, filenames[0]);
             accessor.setFiles(fd, directory, filenames);
         }