Adding an option for peers to negotiate the length of the QUIC

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 0dd3b347b4b0a0e0b245154d36af691e82224d13..d0101c9da8b7c338d839552fceeaed7e679438b3 100644
--- a/net/quic/crypto/crypto_protocol.h
+++ b/net/quic/crypto/crypto_protocol.h
@@ -61,6 +61,11 @@ const QuicTag k1CON = TAG('1', 'C', 'O', 'N');   // Emulate a single connection
 const QuicTag kNACK = TAG('N', 'A', 'C', 'K');   // TCP style nack counting
 const QuicTag kTIME = TAG('T', 'I', 'M', 'E');   // Time based
 
+// Optional support of truncated Connection IDs.  If sent by a peer, the value
+// is the minimum number of bytes allowed for the connection ID sent to the
+// peer.
+const QuicTag kTCID = TAG('T', 'C', 'I', 'D');   // Connection ID truncation.
+
 // FEC options
 const QuicTag kFHDR = TAG('F', 'H', 'D', 'R');   // FEC protect headers