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

ui/aura/window_destruction_observer.h

-// 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.
-
-#ifndef UI_AURA_WINDOW_DESTRUCTION_OBSERVER_H_
-#define UI_AURA_WINDOW_DESTRUCTION_OBSERVER_H_
-
-#include <set>
-
-#include "ui/aura/aura_export.h"
-#include "ui/aura/window.h"
-#include "ui/aura/window_observer.h"
-
-namespace aura {
-
-// A class for observing window (self) destruction. A side effect of a
-// window member funtion may be that the object, i.e. |this|, gets
-// deleted. This class can be used to detect such cases and to exit
-// the member function without any further access to member data. See
-// for example: aura::Window::NotifyWindowVisibilityChangedAtReceiver.
-
-class AURA_EXPORT WindowDestructionObserver : public WindowObserver {
- public:
-  // Addes this observer to window.
-  explicit WindowDestructionObserver(aura::Window* window);
-
-  // Removes this observer from |window_| unless |window_| has been
-  // observed to be destroyed.
-  virtual ~WindowDestructionObserver();
-
-  // Returns true if |window_| has been observed to be destroyed.
-  bool destroyed() const { return destroyed_; }
-
-  private:
-  // aura::WindowObserver overrides:
-  virtual void OnWindowDestroyed(Window* window) OVERRIDE;
-
-  Window* window_;
-  bool destroyed_;
-
-  DISALLOW_COPY_AND_ASSIGN(WindowDestructionObserver);
-};
-
-} // namespace aura
-
-#endif