Only query the absolutely necessary attributes

Since the time taken by g_file_enumerate_children() depends a lot on the
attributes that are queried, we query the minimum attributes that need
to be queired to display the file chooser.

In particular, the attributes for loading the icon are ignored, as icons
are loaded on demand (see previous commit).

gtk/gtkfilechooserdefault.c

@@ -191,6 +191,9 @@ typedef enum {
   SHORTCUT_TYPE_RECENT
 } ShortcutType;
 
+#define MODEL_ATTRIBUTES "standard::name,standard::type,standard::display-name," \
+                         "standard::is-hidden,standard::is-backup,standard::size," \
+                         "standard::content-type,time::modified"
 enum {
   /* the first 3 must be these due to settings caching sort column */
   MODEL_COL_NAME,
@@ -6959,7 +6962,7 @@ set_list_model (GtkFileChooserDefault *impl,
 
   impl->browse_files_model = 
     _gtk_file_system_model_new (impl->current_folder,
-        "standard,time,thumbnail::*",
+        MODEL_ATTRIBUTES,
         file_system_model_set,
         impl,
         MODEL_COL_NUM_COLUMNS,