Remove HistoryItem::m_frameSequenceNumber, it is unused

Source/web/WebHistoryItem.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 141 matching lines @@
 long long WebHistoryItem::documentSequenceNumber() const
 {
     return m_private->documentSequenceNumber();
 }
 
 void WebHistoryItem::setDocumentSequenceNumber(long long documentSequenceNumber)
 {
     m_private->setDocumentSequenceNumber(documentSequenceNumber);
 }
 
-long long WebHistoryItem::frameSequenceNumber() const
-{
-    return m_private->frameSequenceNumber();
-}
-
-void WebHistoryItem::setFrameSequenceNumber(long long frameSequenceNumber)
-{
-    m_private->setFrameSequenceNumber(frameSequenceNumber);
-}
-
 WebHistoryScrollRestorationType WebHistoryItem::scrollRestorationType() const
 {
     return static_cast<WebHistoryScrollRestorationType>(m_private->scrollRestorationType());
 }
 
 void WebHistoryItem::setScrollRestorationType(WebHistoryScrollRestorationType type)
 {
     m_private->setScrollRestorationType(static_cast<HistoryScrollRestorationType>(type));
 }
 
@@ skipping 58 matching lines @@
     m_private = item;
     return *this;
 }
 
 WebHistoryItem::operator PassRefPtrWillBeRawPtr<HistoryItem>() const
 {
     return m_private.get();
 }
 
 } // namespace blink