Remove dead code from childIndex optimization

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index 35321ae41795dcf4958822a763874c9da4123479..dfba38b758b5054691eb02ad7e8562277536526a 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -350,9 +350,6 @@ public:
     void setIsInCanvasSubtree(bool value) { setElementFlag(IsInCanvasSubtree, value); }
     bool isInCanvasSubtree() const { return hasElementFlag(IsInCanvasSubtree); }
 
-    unsigned childIndex() const { return hasRareData() ? rareDataChildIndex() : 0; }
-    void setChildIndex(unsigned);
-
     bool isUpgradedCustomElement() { return customElementState() == Upgraded; }
     bool isUnresolvedCustomElement() { return customElementState() == WaitingForUpgrade; }
 
@@ -633,8 +630,6 @@ private:
 
     QualifiedName m_tagName;
 
-    unsigned rareDataChildIndex() const;
-
     SpellcheckAttributeState spellcheckAttributeState() const;
 
     void updateNamedItemRegistration(const AtomicString& oldName, const AtomicString& newName);