Disable QUIC v29 and earlier. Protected by FLAGS_quic_disable_pre_30.

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 467187d36f74091102e02a668a2f54c77e1fdd97..91fcf8c1f38f800b04cb33041f9b912101f5b3ca 100644
--- a/net/quic/quic_protocol.h
+++ b/net/quic/quic_protocol.h
@@ -390,6 +390,11 @@ typedef std::vector<QuicVersion> QuicVersionVector;
 // Returns a vector of QUIC versions in kSupportedQuicVersions.
 NET_EXPORT_PRIVATE QuicVersionVector QuicSupportedVersions();
 
+// Returns a vector of QUIC versions from |versions| which exclude any versions
+// which are disabled by flags.
+NET_EXPORT_PRIVATE QuicVersionVector
+FilterSupportedVersions(QuicVersionVector versions);
+
 // 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