Dispatch change event for input type=checkbox when checked but value is null

Source/core/html/HTMLInputElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 358 matching lines @@
     void updateValueIfNeeded();
 
     // Returns null if this isn't associated with any radio button group.
     RadioButtonGroupScope* radioButtonGroupScope() const;
     void addToRadioButtonGroup();
     void removeFromRadioButtonGroup();
 #if ENABLE(INPUT_MULTIPLE_FIELDS_UI)
     virtual PassRefPtr<RenderStyle> customStyleForRenderer() OVERRIDE;
 #endif
 
+    virtual bool shouldDispatchFormControlChangeEvent(String&, String&) OVERRIDE;
+
     AtomicString m_name;
     String m_valueIfDirty;
     String m_suggestedValue;
     int m_size;
     int m_maxLength;
     short m_maxResults;
     bool m_isChecked : 1;
     bool m_reflectsCheckedAttribute : 1;
     bool m_isIndeterminate : 1;
     bool m_isActivatedSubmit : 1;
@@ skipping 10 matching lines @@
     RefPtr<InputTypeView> m_inputTypeView;
     // The ImageLoader must be owned by this element because the loader code assumes
     // that it lives as long as its owning element lives. If we move the loader into
     // the ImageInput object we may delete the loader while this element lives on.
     OwnPtr<HTMLImageLoader> m_imageLoader;
     OwnPtr<ListAttributeTargetObserver> m_listAttributeTargetObserver;
 };
 
 } //namespace
 #endif