GTTF: Add missing virtual destructors.

ash/wm/system_modal_container_event_filter_delegate.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_MODALITY_EVENT_FILTER_DELEGATE_H_
 #define ASH_WM_MODALITY_EVENT_FILTER_DELEGATE_H_
 
 #include "ash/ash_export.h"
 
 namespace aura {
 class Window;
 }
 
 namespace ash {
 namespace internal {
 
 class ASH_EXPORT SystemModalContainerEventFilterDelegate {
  public:
+  virtual ~SystemModalContainerEventFilterDelegate() { }
+
   // Returns true if |window| can receive the specified event.
   virtual bool CanWindowReceiveEvents(aura::Window* window) = 0;
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_MODALITY_EVENT_FILTER_DELEGATE_H_