It is time.

ui/views/widget/widget_deletion_observer.h

-// 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.
-
-#ifndef UI_VIEWS_WIDGET_WIDGET_DELETION_OBSERVER_H_
-#define UI_VIEWS_WIDGET_WIDGET_DELETION_OBSERVER_H_
-
-#include "base/basictypes.h"
-#include "base/compiler_specific.h"
-#include "ui/views/views_export.h"
-#include "ui/views/widget/widget_observer.h"
-
-namespace views {
-class Widget;
-
-// A simple WidgetObserver that can be probed for the life of a widget.
-class VIEWS_EXPORT WidgetDeletionObserver : public WidgetObserver {
- public:
-  explicit WidgetDeletionObserver(Widget* widget);
-  virtual ~WidgetDeletionObserver();
-
-  // Returns true if the widget passed in the constructor is still alive.
-  bool IsWidgetAlive() { return widget_ != NULL; }
-
-  // Overridden from WidgetObserver.
-  virtual void OnWidgetDestroying(Widget* widget) override;
-
- private:
-  void CleanupWidget();
-
-  Widget* widget_;
-
-  DISALLOW_COPY_AND_ASSIGN(WidgetDeletionObserver);
-};
-
-}  // namespace views
-
-#endif  // UI_VIEWS_WIDGET_WIDGET_DELETION_OBSERVER_H_