Add experiment selection code for GFE-initiated initial QUIC cwnd.

PiperOrigin-RevId: 245806149
Change-Id: I220c834c691ad5e003756634a116a0e105f7e5f5

quic/core/crypto/crypto_protocol.h

diff --git a/quic/core/crypto/crypto_protocol.h b/quic/core/crypto/crypto_protocol.h
index d9a1ebc..5b65267 100644
--- a/quic/core/crypto/crypto_protocol.h
+++ b/quic/core/crypto/crypto_protocol.h
@@ -188,6 +188,8 @@
 const QuicTag kBWMX = TAG('B', 'W', 'M', 'X');  // Max bandwidth resumption.
 const QuicTag kBWRS = TAG('B', 'W', 'R', 'S');  // Server bandwidth resumption.
 const QuicTag kBWS2 = TAG('B', 'W', 'S', '2');  // Server bw resumption v2.
+const QuicTag kBWS3 = TAG('B', 'W', 'S', '3');  // QUIC Initial CWND - Control.
+const QuicTag kBWS4 = TAG('B', 'W', 'S', '4');  // QUIC Initial CWND - Enabled.
 
 // Enable path MTU discovery experiment.
 const QuicTag kMTUH = TAG('M', 'T', 'U', 'H');  // High-target MTU discovery.