Allow QUIC servers send a TTL for the server config, as opposed to explicit expiration, to mitigate…

net/quic/core/crypto/crypto_protocol.h

Index: net/quic/core/crypto/crypto_protocol.h
diff --git a/net/quic/core/crypto/crypto_protocol.h b/net/quic/core/crypto/crypto_protocol.h
index 28fe6d3873812d6f6b199543cfaca70ca9952bc8..b902f67067181003541ca28f16d22aab02b4acec 100644
--- a/net/quic/core/crypto/crypto_protocol.h
+++ b/net/quic/core/crypto/crypto_protocol.h
@@ -164,6 +164,7 @@ const QuicTag kPROF = TAG('P', 'R', 'O', 'F');   // Proof (signature).
 const QuicTag kCCS  = TAG('C', 'C', 'S', 0);     // Common certificate set
 const QuicTag kCCRT = TAG('C', 'C', 'R', 'T');   // Cached certificate
 const QuicTag kEXPY = TAG('E', 'X', 'P', 'Y');   // Expiry
+const QuicTag kSTTL = TAG('S', 'T', 'T', 'L');   // Server Config TTL
 const QuicTag kSFCW = TAG('S', 'F', 'C', 'W');   // Initial stream flow control
                                                  // receive window.
 const QuicTag kCFCW = TAG('C', 'F', 'C', 'W');   // Initial session/connection