Remove unused focus_window member of MetaCompScreen

Remove some old code; the compositor no longer tracks
the focus window.

http://bugzilla.gnome.org/show_bug.cgi?id=587251

src/compositor/compositor-private.h

@@ -36,7 +36,6 @@ struct _MetaCompScreen
   ClutterActor		*hidden_group;
   GList                 *windows;
   GHashTable            *windows_by_xid;
-  MetaWindow            *focus_window;
   Window                 output;
 
   /* Before we create the output window */

src/compositor/compositor.c

@@ -412,8 +412,6 @@ meta_compositor_manage_screen (MetaCompositor *compositor,
   info->windows = NULL;
   info->windows_by_xid = g_hash_table_new (g_direct_hash, g_direct_equal);
 
-  info->focus_window = meta_display_get_focus_window (display);
-
   meta_screen_set_cm_selection (screen);
 
   info->stage = clutter_stage_get_default ();

src/compositor/mutter-window.c

@@ -1111,9 +1111,6 @@ mutter_window_unmap (MutterWindow *self)
   if (priv->attrs.map_state == IsUnmapped && !priv->needs_unmap)
     return;
 
-  if (priv->window && priv->window == info->focus_window)
-    info->focus_window = NULL;
-
   if (info->switch_workspace_in_progress)
     {
       /*