Make QuicSession::OnFinalByteOffsetReceived virtual.

net/quic/core/quic_session.h

Index: net/quic/core/quic_session.h
diff --git a/net/quic/core/quic_session.h b/net/quic/core/quic_session.h
index 4f8e1efff0e722bd6d830f0dfe0a024f5145a157..7ed5627ba0f40f63ea25743bdcdd03d8534d8831 100644
--- a/net/quic/core/quic_session.h
+++ b/net/quic/core/quic_session.h
@@ -295,8 +295,8 @@ class QUIC_EXPORT_PRIVATE QuicSession : public QuicConnectionVisitorInterface {
   // When this data arrives (via stream frame w. FIN, trailing headers, or RST)
   // this method is called, and correctly updates the connection level flow
   // controller.
-  void OnFinalByteOffsetReceived(QuicStreamId id,
-                                 QuicStreamOffset final_byte_offset);
+  virtual void OnFinalByteOffsetReceived(QuicStreamId id,
+                                         QuicStreamOffset final_byte_offset);
 
   // Return true if given stream is peer initiated.
   bool IsIncomingStream(QuicStreamId id) const;