Removing unused function in NthIndexCache

Source/core/dom/NthIndexCache.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NthIndexCache_h
 #define NthIndexCache_h
 
 #include "core/dom/Element.h"
 #include "core/dom/ElementTraversal.h"
 #include "platform/heap/Handle.h"
@@ skipping 27 matching lines @@
 
         unsigned cacheNthIndices(Element&);
 
         WillBeHeapHashMap<RawPtrWillBeMember<Element>, unsigned> m_elementIndexMap;
         unsigned m_count = 0;
 
         DECLARE_TRACE();
     };
 
     NthIndexData& ensureNthIndexDataFor(Node&);
-    inline unsigned nthIndex(Element&);
 
     using ParentMap = WillBeHeapHashMap<RefPtrWillBeMember<Node>, OwnPtrWillBeMember<NthIndexData>>;
 
     OwnPtrWillBeMember<ParentMap> m_parentMap;
     RawPtrWillBeMember<Document> m_document;
     uint64_t m_domTreeVersion;
 };
 
 inline unsigned NthIndexCache::NthIndexData::nthIndex(Element& element)
 {
@@ skipping 23 matching lines @@
 
 inline unsigned NthIndexCache::nthLastChildIndex(Element& element)
 {
     ASSERT(element.parentNode());
     return ensureNthIndexDataFor(*element.parentNode()).nthLastIndex(element);
 }
 
 } // namespace blink
 
 #endif // NthIndexCache_h