Nukes aura::WindowDestructionObserver. It's effectively the same as

ui/aura/window_destruction_observer.cc

Index: ui/aura/window_destruction_observer.cc
diff --git a/ui/aura/window_destruction_observer.cc b/ui/aura/window_destruction_observer.cc
deleted file mode 100644
index 20325c7bc5f166147cd10257d468cd524b4096fe..0000000000000000000000000000000000000000
--- a/ui/aura/window_destruction_observer.cc
+++ /dev/null
@@ -1,25 +0,0 @@
-// Copyright 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/window_destruction_observer.h"
-
-namespace aura {
-
-WindowDestructionObserver::WindowDestructionObserver(Window* window)
-    : window_(window), destroyed_(false) {
-  DCHECK(window_);
-  window_->AddObserver(this);
-}
-
-WindowDestructionObserver::~WindowDestructionObserver() {
-  if (!destroyed_)
-    window_->RemoveObserver(this);
-}
-
-void WindowDestructionObserver::OnWindowDestroyed(Window* window) {
-  if (window == window_)
-    destroyed_ = true;
-}
-
-} // namespace aura