Use a weak pointer to determine if resizer was destroyed by nested Drag calls.

ash/wm/dock/docked_window_resizer.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 ASH_WM_DOCK_DOCK_WINDOW_RESIZER_H_
 #define ASH_WM_DOCK_DOCK_WINDOW_RESIZER_H_
 
 #include "ash/wm/dock/dock_types.h"
 #include "ash/wm/window_resizer.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 
 namespace gfx {
 class Point;
 class Rect;
 }
 
 namespace aura {
 class RootWindow;
 }
 
@@ skipping 69 matching lines @@
 
   // Gives a preview of where the the window will end up.
   scoped_ptr<PhantomWindowController> snap_phantom_window_controller_;
 
   // Set to true if the window that is being dragged was docked before drag.
   bool was_docked_;
 
   // True if the dragged window is docked during the drag.
   bool is_docked_;
 
-  // If non-NULL the destructor sets this to true. Used to determine if this has
-  // been deleted.
-  bool* destroyed_;
+  base::WeakPtrFactory<DockedWindowResizer> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DockedWindowResizer);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_DOCK_DOCK_WINDOW_RESIZER_H_