Include the socket receive buffer in the connection handshake.

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 edaea2f75b9f686b74d1be026545e019bcaea74a..878b8eefb2b8a260c9f1780fbedfff914bdd1fbc 100644
--- a/net/quic/crypto/crypto_protocol.h
+++ b/net/quic/crypto/crypto_protocol.h
@@ -44,6 +44,9 @@ const QuicTag kNULL = TAG('N', 'U', 'L', 'N');   // null algorithm
 const QuicTag kAESG = TAG('A', 'E', 'S', 'G');   // AES128 + GCM-12
 const QuicTag kCC12 = TAG('C', 'C', '1', '2');   // ChaCha20 + Poly1305
 
+// Socket receive buffer
+const QuicTag kSRBF = TAG('S', 'R', 'B', 'F');   // Socket receive buffer
+
 // Congestion control feedback types
 const QuicTag kQBIC = TAG('Q', 'B', 'I', 'C');   // TCP cubic
 const QuicTag kPACE = TAG('P', 'A', 'C', 'E');   // Paced TCP cubic