Add a frame sequence number to HistoryItem

Source/core/loader/HistoryItem.h

Index: Source/core/loader/HistoryItem.h
diff --git a/Source/core/loader/HistoryItem.h b/Source/core/loader/HistoryItem.h
index 80a31cb4dbfe128e925733de7646978127b613a2..018e5db24463535ed1065e285efffac89b78bbb2 100644
--- a/Source/core/loader/HistoryItem.h
+++ b/Source/core/loader/HistoryItem.h
@@ -94,6 +94,9 @@ public:
     void setDocumentSequenceNumber(long long number) { m_documentSequenceNumber = number; }
     long long documentSequenceNumber() const { return m_documentSequenceNumber; }
 
+    void setFrameSequenceNumber(long long number) { m_frameSequenceNumber = number; }
+    long long frameSequenceNumber() const { return m_frameSequenceNumber; }
+
     void setFormInfoFromRequest(const ResourceRequest&);
     void setFormData(PassRefPtr<FormData>);
     void setFormContentType(const AtomicString&);
@@ -124,6 +127,10 @@ private:
     // such HistoryItem to another preserves the document.
     int64_t m_documentSequenceNumber;
 
+    // Used to match frames across serialization/deserialization more reliably

[darin (slow to review), 2014/07/25 04:39:06]

I think it would be more helpful to add a comment here that defines the new
field, similar to the definitions for the other sequence numbers. What does
frame sequence number represent? How does it evolve, etc.?

+    // than is possible using unique names.
+    int64_t m_frameSequenceNumber;
+
     // Support for HTML5 History
     RefPtr<SerializedScriptValue> m_stateObject;