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..02637f315e4d636fce919a8a99cd00d11552fbee 100644
--- a/ui/views/widget/native_widget_private.h
+++ b/ui/views/widget/native_widget_private.h
@@ -100,6 +100,13 @@ class VIEWS_EXPORT NativeWidgetPrivate : public NativeWidget {
   // Returns the NativeWidget's layer, if any.
   virtual ui::Layer* GetLayer() = 0;
 
+  // Reorder the widget's child layers which belong to NativeViews attached to
+  // the view tree (eg via a NativeViewHost). The layers are reordered to match
+  // the order of views with layers / views with attached layers in the view
+  // tree. This method assumes that the layers which are owned by views are
+  // already correctly ordered relative to each other.
+  virtual void ReorderLayersForAttachedNativeViews() = 0;
+
   // Notifies the NativeWidget that a view was removed from the Widget's view
   // hierarchy.
   virtual void ViewRemoved(View* view) = 0;