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

net/quic/crypto/quic_crypto_client_config.h

Index: net/quic/crypto/quic_crypto_client_config.h
diff --git a/net/quic/crypto/quic_crypto_client_config.h b/net/quic/crypto/quic_crypto_client_config.h
index 9c722db5e5f9401d5f4981cb95d4b071a9affcd0..06925ac426d6479df752e91fc7a84199814b9b2a 100644
--- a/net/quic/crypto/quic_crypto_client_config.h
+++ b/net/quic/crypto/quic_crypto_client_config.h
@@ -208,6 +208,18 @@ class NET_EXPORT_PRIVATE QuicCryptoClientConfig : public QuicCryptoConfig {
                                    QuicCryptoNegotiatedParameters* out_params,
                                    std::string* error_details);
 
+  // Processes the message in |server_update|, updating the cached source
+  // address token, and server config.
+  // If |server_update| is invalid then |error_details| will contain an error
+  // message, and an error code will be returned. If all has gone well
+  // QUIC_NO_ERROR is returned.
+  QuicErrorCode ProcessServerConfigUpdate(
+      const CryptoHandshakeMessage& server_update,
+      QuicWallTime now,
+      CachedState* cached,
+      QuicCryptoNegotiatedParameters* out_params,
+      std::string* error_details);
+
   ProofVerifier* proof_verifier() const;
 
   // SetProofVerifier takes ownership of a |ProofVerifier| that clients are