1 files changed, 13 insertions, 2 deletions
diff --git a/Source/WebCore/history/HistoryItem.h b/Source/WebCore/history/HistoryItem.h
index a4622c0..526cae2 100644
--- a/Source/WebCore/history/HistoryItem.h
+++ b/Source/WebCore/history/HistoryItem.h
@@ -88,6 +88,9 @@ public:
 
     PassRefPtr<HistoryItem> copy() const;
 
+    // Resets the HistoryItem to its initial state, as returned by create().
+    void reset();
+    
     void encodeBackForwardTree(Encoder&) const;
     static PassRefPtr<HistoryItem> decodeBackForwardTree(const String& urlString, const String& title, const String& originalURLString, Decoder&);
 
@@ -148,7 +151,7 @@ public:
 
     void setDocumentSequenceNumber(long long number) { m_documentSequenceNumber = number; }
     long long documentSequenceNumber() const { return m_documentSequenceNumber; }
-    
+
     void setFormInfoFromRequest(const ResourceRequest&);
     void setFormData(PassRefPtr<FormData>);
     void setFormContentType(const String&);
@@ -262,11 +265,19 @@ private:
 
     OwnPtr<Vector<String> > m_redirectURLs;
 
+    // If two HistoryItems have the same item sequence number, then they are
+    // 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;
+
     // Support for HTML5 History
     RefPtr<SerializedScriptValue> m_stateObject;
-    int64_t m_documentSequenceNumber;
     
     // info used to repost form data
     RefPtr<FormData> m_formData;