Add a unique frame id and save it on HistoryItem.

Source/core/history/HistoryItem.h

 /*
  * Copyright (C) 2006, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Research In Motion Limited. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 73 matching lines @@
 
     void setStateObject(PassRefPtr<SerializedScriptValue> object);
     SerializedScriptValue* stateObject() const { return m_stateObject.get(); }
 
     void setItemSequenceNumber(long long number) { m_itemSequenceNumber = number; }
     long long itemSequenceNumber() const { return m_itemSequenceNumber; }
 
     void setDocumentSequenceNumber(long long number) { m_documentSequenceNumber = number; }
     long long documentSequenceNumber() const { return m_documentSequenceNumber; }
 
+    void setTargetFrameID(int64_t id) { m_targetFrameID = id; }
+    int64_t targetFrameID() const { return m_targetFrameID; }
+
     void setFormInfoFromRequest(const ResourceRequest&);
     void setFormData(PassRefPtr<FormData>);
     void setFormContentType(const String&);
 
     void addChildItem(PassRefPtr<HistoryItem>);
     void setChildItem(PassRefPtr<HistoryItem>);
     HistoryItem* childItemWithTarget(const String&) const;
     HistoryItem* childItemWithDocumentSequenceNumber(long long number) const;
     const HistoryItemVector& children() const;
     void clearChildren();
@@ skipping 29 matching lines @@
     // clones of one another.  Traversing history from one such HistoryItem to
     // another is a no-op.  HistoryItem clones are created for parent and
     // sibling frames when only a subframe navigates.
     int64_t m_itemSequenceNumber;
 
     // If two HistoryItems have the same document sequence number, then they
     // refer to the same instance of a document.  Traversing history from one
     // such HistoryItem to another preserves the document.
     int64_t m_documentSequenceNumber;
 
+    int64_t m_targetFrameID;
+
     // Support for HTML5 History
     RefPtr<SerializedScriptValue> m_stateObject;
 
     // info used to repost form data
     RefPtr<FormData> m_formData;
     String m_formContentType;
 
 }; //class HistoryItem
 
 } //namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 extern "C" int showTree(const WebCore::HistoryItem*);
 #endif
 
 #endif // HISTORYITEM_H