Remove unused InvalidateOnItemAttrChange NodeList invalidation type

Source/core/dom/LiveNodeList.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2006, 2007 Apple Inc. 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 99 matching lines @@
         return attrName == HTMLNames::nameAttr;
     case InvalidateOnIdNameAttrChange:
         return attrName == HTMLNames::idAttr || attrName == HTMLNames::nameAttr;
     case InvalidateOnForAttrChange:
         return attrName == HTMLNames::forAttr;
     case InvalidateForFormControls:
         return attrName == HTMLNames::nameAttr || attrName == HTMLNames::idAttr || attrName == HTMLNames::forAttr
             || attrName == HTMLNames::formAttr || attrName == HTMLNames::typeAttr;
     case InvalidateOnHRefAttrChange:
         return attrName == HTMLNames::hrefAttr;
-    case InvalidateOnItemAttrChange:
     case DoNotInvalidateOnAttributeChanges:
         return false;
     case InvalidateOnAnyAttrChange:
         return true;
     }
     return false;
 }
 
 class LiveNodeList : public NodeList, public LiveNodeListBase {
 public:
@@ skipping 19 matching lines @@
 
 private:
     virtual bool isLiveNodeList() const OVERRIDE FINAL { return true; }
 
     mutable CollectionIndexCache<LiveNodeList, Element> m_collectionIndexCache;
 };
 
 } // namespace WebCore
 
 #endif // LiveNodeList_h