Add QUIC 31 in which the server's proof covers both the static server config as well as a hash of t…

net/quic/crypto/crypto_protocol.h

Index: net/quic/crypto/crypto_protocol.h
diff --git a/net/quic/crypto/crypto_protocol.h b/net/quic/crypto/crypto_protocol.h
index 5d2f71f57a974b03b8841759bd40511cd01bbdfe..a945458f9d23a4db6e6e7842a2da8183279c0622 100644
--- a/net/quic/crypto/crypto_protocol.h
+++ b/net/quic/crypto/crypto_protocol.h
@@ -213,7 +213,12 @@ const size_t kOrbitSize = 8;  // Number of bytes in an orbit value.
 
 // kProofSignatureLabel is prepended to server configs before signing to avoid
 // any cross-protocol attacks on the signature.
-const char kProofSignatureLabel[] = "QUIC server config signature";
+// TODO(rch): Remove this when QUIC_VERSION_30 is removed.
+const char kProofSignatureLabelOld[] = "QUIC server config signature";
+
+// kProofSignatureLabel is prepended to the CHLO hash and server configs before
+// signing to avoid any cross-protocol attacks on the signature.
+const char kProofSignatureLabel[] = "QUIC CHLO and server config signature";
 
 // kClientHelloMinimumSize is the minimum size of a client hello. Client hellos
 // will have PAD tags added in order to ensure this minimum is met and client