Remove redundant m_isItemCacheValid flag from LiveNodeListBase

Source/core/html/HTMLCollection.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2011, 2012 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 28 matching lines @@
 
     // DOM API
     virtual Node* namedItem(const AtomicString& name) const;
 
     // Non-DOM API
     void namedItems(const AtomicString& name, Vector<RefPtr<Node> >&) const;
     bool isEmpty() const
     {
         if (isLengthCacheValid())
             return !cachedLength();
-        if (isItemCacheValid())
-            return !cachedItem();
+        if (cachedItem())
+            return false;
         return !item(0);
     }
     bool hasExactlyOneItem() const
     {
         if (isLengthCacheValid())
             return cachedLength() == 1;
-        if (isItemCacheValid())
-            return cachedItem() && !cachedItemOffset() && !item(1);
+        if (cachedItem())
+            return !cachedItemOffset() && !item(1);
         return item(0) && !item(1);
     }
 
     virtual Element* virtualItemAfter(Element*) const;
 
     Element* traverseToFirstElement(ContainerNode& root) const;
     Element* traverseForwardToOffset(unsigned offset, Element& currentElement, unsigned& currentOffset, ContainerNode* root) const;
 
 protected:
     HTMLCollection(Node* base, CollectionType, ItemAfterOverrideType);
@@ skipping 23 matching lines @@
     mutable unsigned m_isNameCacheValid : 1;
     mutable NodeCacheMap m_idCache;
     mutable NodeCacheMap m_nameCache;
 
     friend class LiveNodeListBase;
 };
 
 } // namespace
 
 #endif