Add VersionOfIndex() to quic_protocol.h

net/quic/core/quic_protocol.h

Index: net/quic/core/quic_protocol.h
diff --git a/net/quic/core/quic_protocol.h b/net/quic/core/quic_protocol.h
index 0ac0b334b5a0653ba252c2a73c98f739911055a5..34e6a407267f8a900e407b6f44bf34d5d374622c 100644
--- a/net/quic/core/quic_protocol.h
+++ b/net/quic/core/quic_protocol.h
@@ -394,6 +394,11 @@ NET_EXPORT_PRIVATE QuicVersionVector QuicSupportedVersions();
 NET_EXPORT_PRIVATE QuicVersionVector
 FilterSupportedVersions(QuicVersionVector versions);
 
+// Returns QUIC version of |index| in result of |versions|. Returns
+// QUIC_VERSION_UNSUPPORTED if |index| is out of bounds.
+NET_EXPORT_PRIVATE QuicVersionVector
+VersionOfIndex(const QuicVersionVector& versions, int index);
+
 // QuicTag is written to and read from the wire, but we prefer to use
 // the more readable QuicVersion at other levels.
 // Helper function which translates from a QuicVersion to a QuicTag. Returns 0