Allow QUIC clients to accept STK/SCFG updates on an existing connection.

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 c887e07793e7f7b1c318b70f3a65fb354c4ec784..4481a9486b03fb1a8df944593645e0916f356d80 100644
--- a/net/quic/crypto/quic_crypto_client_config.cc
+++ b/net/quic/crypto/quic_crypto_client_config.cc
@@ -703,6 +703,23 @@ QuicErrorCode QuicCryptoClientConfig::ProcessServerHello(
   return QUIC_NO_ERROR;
 }
 
+QuicErrorCode QuicCryptoClientConfig::ProcessServerConfigUpdate(
+    const CryptoHandshakeMessage& server_config_update,
+    QuicWallTime now,
+    CachedState* cached,
+    QuicCryptoNegotiatedParameters* out_params,
+    string* error_details) {
+  DCHECK(error_details != NULL);
+
+  if (server_config_update.tag() != kSCUP) {
+    *error_details = "ServerConfigUpdate must have kSCUP tag.";
+    return QUIC_INVALID_CRYPTO_MESSAGE_TYPE;
+  }
+
+  return CacheNewServerConfig(server_config_update, now, cached, out_params,
+                              error_details);
+}
+
 ProofVerifier* QuicCryptoClientConfig::proof_verifier() const {
   return proof_verifier_.get();
 }