Observe for window's (self) deletion during activation/focus change

ui/aura/window_destruction_observer.h

Index: ui/aura/window_destruction_observer.h
diff --git a/ui/aura/window_destruction_observer.h b/ui/aura/window_destruction_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..53c4a05bcaef182a55a4d8b98d241541475cb1d9
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+++ b/ui/aura/window_destruction_observer.h
@@ -0,0 +1,46 @@
+// 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.
+  WindowDestructionObserver(aura::Window* window);

[Ben Goodger (Google), 2013/03/19 22:55:58]

explicit

[sschmitz, 2013/03/19 23:11:06]

Done.

+
+  // 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;

[Ben Goodger (Google), 2013/03/19 22:55:58]

you can just inline this impl here

[sschmitz, 2013/03/19 23:11:06]

Done.

+
+  private:
+  // aura::WindowObserver overrides:
+  virtual void OnWindowDestroyed(Window* window) OVERRIDE;
+
+  Window* window_;
+  bool destroyed_;
+
+  DISALLOW_COPY_AND_ASSIGN(WindowDestructionObserver);
+};
+
+} // namespace aura
+
+#endif