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

ui/aura/window.h

 // Copyright (c) 2012 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_H_
 #define UI_AURA_WINDOW_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 410 matching lines @@
   // Notifies this window and its parent hierarchy.
   void NotifyWindowHierarchyChangeUp(
       const WindowObserver::HierarchyChangeParams& params);
   // Notifies this window's observers.
   void NotifyWindowHierarchyChangeAtReceiver(
       const WindowObserver::HierarchyChangeParams& params);
 
   // Methods implementing visibility change notifications. See WindowObserver
   // for more details.
   void NotifyWindowVisibilityChanged(aura::Window* target, bool visible);
-  // Notifies this window's observers.
-  void NotifyWindowVisibilityChangedAtReceiver(aura::Window* target,
+  // Notifies this window's observers. Returns false if |this| was deleted
+  // during the call (by an observer), otherwise true.
+  bool NotifyWindowVisibilityChangedAtReceiver(aura::Window* target,
                                                bool visible);
-  // Notifies this window and its child hierarchy.
-  void NotifyWindowVisibilityChangedDown(aura::Window* target, bool visible);
+  // Notifies this window and its child hierarchy. Returns false if
+  // |this| was deleted during the call (by an observer), otherwise
+  // true.
+  bool NotifyWindowVisibilityChangedDown(aura::Window* target, bool visible);
   // Notifies this window and its parent hierarchy.
   void NotifyWindowVisibilityChangedUp(aura::Window* target, bool visible);
 
   // Invoked from the closure returned by PrepareForLayerBoundsChange() after
   // the bounds of the layer has changed. |old_bounds| is the previous bounds of
   // the layer, and |contained_mouse| is true if the mouse was previously within
   // the window's bounds.
   void OnLayerBoundsChanged(const gfx::Rect& old_bounds, bool contained_mouse);
 
   // Overridden from ui::LayerDelegate:
@@ skipping 67 matching lines @@
   };
 
   std::map<const void*, Value> prop_map_;
 
   DISALLOW_COPY_AND_ASSIGN(Window);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_H_