Remove dead code from childIndex optimization

Source/core/dom/ElementRareData.h

 /*
  * Copyright (C) 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 David Smith <catfish.man@gmail.com>
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 45 matching lines @@
         m_tabindex = index;
         setElementFlag(TabIndexWasSetExplicitly, true);
     }
 
     void clearTabIndexExplicitly()
     {
         m_tabindex = 0;
         clearElementFlag(TabIndexWasSetExplicitly);
     }
 
-    unsigned childIndex() const { return m_childIndex; }
-    void setChildIndex(unsigned index) { m_childIndex = index; }
-
     CSSStyleDeclaration& ensureInlineCSSStyleDeclaration(Element* ownerElement);
 
     void clearShadow() { m_shadow = nullptr; }
     ElementShadow* shadow() const { return m_shadow.get(); }
     ElementShadow& ensureShadow()
     {
         if (!m_shadow)
             m_shadow = ElementShadow::create();
         return *m_shadow;
     }
@@ skipping 38 matching lines @@
     }
 
     bool hasPseudoElements() const;
     void clearPseudoElements();
 
     void setCustomElementDefinition(PassRefPtr<CustomElementDefinition> definition) { m_customElementDefinition = definition; }
     CustomElementDefinition* customElementDefinition() const { return m_customElementDefinition.get(); }
 
 private:
     short m_tabindex;
-    unsigned short m_childIndex;
 
     LayoutSize m_minimumSizeForResizing;
     IntSize m_savedLayerScrollOffset;
 
     OwnPtr<DatasetDOMStringMap> m_dataset;
     OwnPtr<ClassList> m_classList;
     OwnPtr<ElementShadow> m_shadow;
     OwnPtr<NamedNodeMap> m_attributeMap;
     OwnPtr<InputMethodContext> m_inputMethodContext;
     OwnPtrWillBePersistent<ActiveAnimations> m_activeAnimations;
@@ skipping 10 matching lines @@
 };
 
 inline IntSize defaultMinimumSizeForResizing()
 {
     return IntSize(LayoutUnit::max(), LayoutUnit::max());
 }
 
 inline ElementRareData::ElementRareData(RenderObject* renderer)
     : NodeRareData(renderer)
     , m_tabindex(0)
-    , m_childIndex(0)
     , m_minimumSizeForResizing(defaultMinimumSizeForResizing())
 {
 }
 
 inline ElementRareData::~ElementRareData()
 {
     ASSERT(!m_shadow);
     ASSERT(!m_generatedBefore);
     ASSERT(!m_generatedAfter);
     ASSERT(!m_backdrop);
@@ skipping 44 matching lines @@
     case BACKDROP:
         return m_backdrop.get();
     default:
         return 0;
     }
 }
 
 inline void ElementRareData::resetStyleState()
 {
     clearElementFlag(StyleAffectedByEmpty);
-    setChildIndex(0);
 }
 
 } // namespace
 
 #endif // ElementRareData_h