It is time.

ui/aura/client/window_stacking_client.cc

Index: ui/aura/client/window_stacking_client.cc
diff --git a/ui/aura/client/window_stacking_client.cc b/ui/aura/client/window_stacking_client.cc
deleted file mode 100644
index 8f909766d64205458e9fc424ac1ac0b308f308f0..0000000000000000000000000000000000000000
--- a/ui/aura/client/window_stacking_client.cc
+++ /dev/null
@@ -1,25 +0,0 @@
-// Copyright (c) 2013 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "ui/aura/client/window_stacking_client.h"
-
-namespace aura {
-namespace client {
-
-namespace {
-
-WindowStackingClient* instance = NULL;
-
-}  // namespace
-
-void SetWindowStackingClient(WindowStackingClient* client) {
-  instance = client;
-}
-
-WindowStackingClient* GetWindowStackingClient() {
-  return instance;
-}
-
-}  // namespace client
-}  // namespace aura