Reorder the NativeViews attached to a view via kViewHostKey according to the position of the view

ui/views/widget/native_widget_private.h

Index: ui/views/widget/native_widget_private.h
diff --git a/ui/views/widget/native_widget_private.h b/ui/views/widget/native_widget_private.h
index 2bb61c0bb5321281ea7409405fb4aec3f24a5886..b9cc7af0d23aa7ce394e8114cc32088de7f24fe8 100644
--- a/ui/views/widget/native_widget_private.h
+++ b/ui/views/widget/native_widget_private.h
@@ -100,6 +100,15 @@ class VIEWS_EXPORT NativeWidgetPrivate : public NativeWidget {
   // Returns the NativeWidget's layer, if any.
   virtual ui::Layer* GetLayer() = 0;
 
+  // Reorders the widget's child NativeViews which are associated to the view
+  // tree (eg via a NativeViewHost) to match the z-order of the views in the
+  // view tree. The z-order of views with layers relative to views with
+  // associated NativeViews is used to reorder the NativeView layers. This
+  // method assumes that the widget's child layers which are owned by a view are
+  // already in the correct z-order relative to each other and does no
+  // reordering if there are no views with an associated NativeView.
+  virtual void ReorderNativeViews() = 0;
+
   // Notifies the NativeWidget that a view was removed from the Widget's view
   // hierarchy.
   virtual void ViewRemoved(View* view) = 0;