Remove (Native)Widget::StackBelow().

ui/views/widget/desktop_aura/desktop_native_widget_aura.cc

Index: ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
diff --git a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
index 35f4e2ea20cbed7de50630de7480cd4bc609b134..b3d06cfd2f846657ae4a7d03f318bb937676496c 100644
--- a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
+++ b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
@@ -689,9 +689,6 @@ void DesktopNativeWidgetAura::StackAtTop() {
     desktop_window_tree_host_->StackAtTop();
 }
 
-void DesktopNativeWidgetAura::StackBelow(gfx::NativeView native_view) {
-}
-
 void DesktopNativeWidgetAura::SetShape(std::unique_ptr<SkRegion> shape) {
   if (content_window_)
     desktop_window_tree_host_->SetShape(std::move(shape));