window: Do not unfocus on new window

mutter would remove focus from a toplevel when showing one of its
transient window which is not on top and not focused.

When using xdg_popup without grab as allowed in xdg_shell v6, the popup
wouldn't be focused, and if an intermediate event occurs before the
popup is shown, it's not placed on top either, which could randomly
trigger a loss of focus in the corresponding toplevel window.

Remove that special case, it doesn't make much sense to globally unset
focus when mapping a new window.

https://bugzilla.gnome.org/show_bug.cgi?id=773210
GNOME/mutter@998d921#diff-029d285c3238fbe60d57f513265e1723

Author: clefebvre

src/core/window.c

@@ -3040,27 +3040,7 @@ meta_window_show (MetaWindow *window)
       ( (!place_on_top_on_map && !takes_focus_on_map) ||
       window_would_be_covered (window) )
     ) {
-      if (meta_window_is_ancestor_of_transient (focus_window, window))
-        {
-          guint32     timestamp;
-
-          timestamp = meta_display_get_current_time_roundtrip (window->display);
-
-          /* This happens for error dialogs or alerts; these need to remain on
-           * top, but it would be confusing to have its ancestor remain
-           * focused.
-           */
-          meta_topic (META_DEBUG_STARTUP,
-                      "The focus window %s is an ancestor of the newly mapped "
-                      "window %s which isn't being focused.  Unfocusing the "
-                      "ancestor.\n",
-                      focus_window->desc, window->desc);
-
-          meta_display_focus_the_no_focus_window (window->display,
-                                                  window->screen,
-                                                  timestamp);
-        }
-      else
+      if (!meta_window_is_ancestor_of_transient (focus_window, window))
         {
           needs_stacking_adjustment = TRUE;
           if (!window->placed)