window-list/gwl: Simplify window focus updates.

Instead of starting at the primary window and iterating thru
transients to check for focus, check the MetaDisplay's focus-window
to see if the primary window is an ancestor.

Cjs seems to have an issue nesting the meta_window_foreach_transient
closure inside the notify closure for the window 'appears-focused'
property. This causes a reference count warning for GClosure, and
occasionally a crash.

This is reproducible with a normal GtkDialog with a transient
parent set, and toggle the window list item for the application.

Author: mtwebster

files/usr/share/cinnamon/applets/[email protected]/appGroup.js

@@ -54,15 +54,10 @@ const getFocusState = function(metaWindow) {
         return true;
     }
 
-    let transientHasFocus = false;
-    metaWindow.foreach_transient(function(transient) {
-        if (transient && transient.appears_focused) {
-            transientHasFocus = true;
-            return false;
-        }
+    if (global.display.focus_window && metaWindow.is_ancestor_of_transient(global.display.focus_window))
         return true;
-    });
-    return transientHasFocus;
+
+    return false;
 };
 
 class AppGroup {

files/usr/share/cinnamon/applets/[email protected]/applet.js

@@ -553,21 +553,16 @@ class AppMenuButton {
     }
 
     _hasFocus() {
-        if (this.metaWindow.minimized)
+        if (!this.metaWindow || this.metaWindow.minimized)
             return false;
 
         if (this.metaWindow.has_focus())
             return true;
 
-        let transientHasFocus = false;
-        this.metaWindow.foreach_transient(function(transient) {
-            if (transient.has_focus()) {
-                transientHasFocus = true;
-                return false;
-            }
+        if (global.display.focus_window && this.metaWindow.is_ancestor_of_transient(global.display.focus_window))
             return true;
-        });
-        return transientHasFocus;
+
+        return false
     }
 
     onFocus() {