Change the null value for packet sequence numbers to

net/quic/quic_protocol.h

Index: net/quic/quic_protocol.h
diff --git a/net/quic/quic_protocol.h b/net/quic/quic_protocol.h
index 7d33a8a437b21611974ba9fd1365382fcc7a7212..b01abea9d08697f783ea9164ef9920dd7d1ea62e 100644
--- a/net/quic/quic_protocol.h
+++ b/net/quic/quic_protocol.h
@@ -592,6 +592,9 @@ struct NET_EXPORT_PRIVATE QuicPacketPublicHeader {
   QuicVersionVector versions;
 };
 
+// An integer which cannot be a packet sequence number.
+const QuicPacketSequenceNumber kInvalidPacketSequenceNumber = 0;
+
 // Header for Data or FEC packets.
 struct NET_EXPORT_PRIVATE QuicPacketHeader {
   QuicPacketHeader();