Add a unique frame id and save it on HistoryItem.

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 170 matching lines @@
 {
     return m_private->documentSequenceNumber();
 }
 
 void WebHistoryItem::setDocumentSequenceNumber(long long documentSequenceNumber)
 {
     ensureMutable();
     m_private->setDocumentSequenceNumber(documentSequenceNumber);
 }
 
+long long WebHistoryItem::targetFrameID() const
+{
+    return m_private->targetFrameID();
+}
+
+void WebHistoryItem::setTargetFrameID(long long targetFrameID)
+{
+    ensureMutable();
+    m_private->setTargetFrameID(targetFrameID);
+}
+
 WebSerializedScriptValue WebHistoryItem::stateObject() const
 {
     return WebSerializedScriptValue(m_private->stateObject());
 }
 
 void WebHistoryItem::setStateObject(const WebSerializedScriptValue& object)
 {
     ensureMutable();
     m_private->setStateObject(object);
 }
@@ skipping 57 matching lines @@
     return m_private.get();
 }
 
 void WebHistoryItem::ensureMutable()
 {
     if (!m_private->hasOneRef())
         m_private = m_private->copy();
 }
 
 } // namespace WebKit