Desktop aura: Break aura::Window::SetParent in two.

ash/wm/gestures/long_press_affordance_handler.cc

Index: ash/wm/gestures/long_press_affordance_handler.cc
diff --git a/ash/wm/gestures/long_press_affordance_handler.cc b/ash/wm/gestures/long_press_affordance_handler.cc
index 112a97ed4fe2b697810b20dc7c1ddf5d398f7142..25d3a4dcea3a377590549efea307dc89751a3893 100644
--- a/ash/wm/gestures/long_press_affordance_handler.cc
+++ b/ash/wm/gestures/long_press_affordance_handler.cc
@@ -68,9 +68,9 @@ views::Widget* CreateAffordanceWidget(aura::RootWindow* root_window) {
   params.transparent = true;
   widget->Init(params);
   widget->SetOpacity(0xFF);
-  widget->GetNativeWindow()->SetParent(
-      ash::GetRootWindowController(root_window)->GetContainer(
-          ash::internal::kShellWindowId_OverlayContainer));
+  ash::GetRootWindowController(root_window)->GetContainer(
+      ash::internal::kShellWindowId_OverlayContainer)->AddChild(
+          widget->GetNativeWindow());
   return widget;
 }