Along with sending the SCUP message, this CL includes small fixes which

net/quic/crypto/quic_crypto_client_config.cc

Index: net/quic/crypto/quic_crypto_client_config.cc
diff --git a/net/quic/crypto/quic_crypto_client_config.cc b/net/quic/crypto/quic_crypto_client_config.cc
index d00e67677df1c62763bf662f04d2c9ed28a8dc51..4ede2c6d812994d975e1d2876a0ba5c9ae383396 100644
--- a/net/quic/crypto/quic_crypto_client_config.cc
+++ b/net/quic/crypto/quic_crypto_client_config.cc
@@ -611,7 +611,12 @@ QuicErrorCode QuicCryptoClientConfig::CacheNewServerConfig(
 
     cached->SetProof(certs, proof);
   } else {
-    cached->ClearProof();
+    if (proof_verifier() != NULL) {
+      // Secure QUIC: clear existing proof as we have been sent a new SCFG
+      // without matching proof/certs.
+      cached->ClearProof();
+    }
+
     if (has_proof && !has_cert) {
       *error_details = "Certificate missing";
       return QUIC_INVALID_CRYPTO_MESSAGE_PARAMETER;