Allow fixed (non-negotiated) values to be sent in QUIC CHLO/SHLO. Also

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 8c6dcb926c15207ef6068b34d1f01ef74b193c6e..80f34d7bb2bc5259af456a9dd56d3cb9a1024a52 100644
--- a/net/quic/crypto/crypto_protocol.h
+++ b/net/quic/crypto/crypto_protocol.h
@@ -82,6 +82,8 @@ 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 kIFCW = TAG('I', 'F', 'C', 'W');  // Initial flow control receive
+                                                // window.
 
 // Server hello tags
 const QuicTag kCADR = TAG('C', 'A', 'D', 'R');  // Client IP address and port