Fix crash if window is destroyed while dragging it.

ash/wm/window_resizer.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 ASH_WM_WINDOW_RESIZER_H_
 #define ASH_WM_WINDOW_RESIZER_H_
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "ui/gfx/rect.h"
@@ skipping 39 matching lines @@
   // of the window supplied to the constructor. |event_flags| is the event
   // flags from the event.
   virtual void Drag(const gfx::Point& location, int event_flags) = 0;
 
   // Invoked to complete the drag.
   virtual void CompleteDrag(int event_flags) = 0;
 
   // Reverts the drag.
   virtual void RevertDrag() = 0;
 
+  // Returns the target window the resizer was created for.
+  virtual aura::Window* GetTarget() = 0;
+
  protected:
   struct Details {
     Details();
     Details(aura::Window* window,
             const gfx::Point& location,
             int window_component);
     ~Details();
 
     // The window we're resizing.
     aura::Window* window;
@@ skipping 55 matching lines @@
   // Returns the height of the drag.
   static int GetHeightForDrag(const Details& details,
                               int min_height,
                               int* delta_y,
                               int grid_size);
 };
 
 }  // namespace aura
 
 #endif  // ASH_WM_WINDOW_RESIZER_H_