Deprecate FLAGS_quic_default_immediate_forward_secure.

net/quic/quic_flags.cc

Index: net/quic/quic_flags.cc
diff --git a/net/quic/quic_flags.cc b/net/quic/quic_flags.cc
index e135ef4770e6cc91bd35b9bb5dd0a3b94f247bff..b054d87113f22a13271d363d1d20b38df399313d 100644
--- a/net/quic/quic_flags.cc
+++ b/net/quic/quic_flags.cc
@@ -97,11 +97,6 @@ bool FLAGS_quic_use_cheap_stateless_rejects = false;
 // than QuicTimes.
 bool FLAGS_quic_socket_walltimestamps = true;
 
-// If true, default to immediate forward secure once established on the
-// server side, and the IPFS connection option disables this instead of
-// enabling it.
-bool FLAGS_quic_default_immediate_forward_secure = true;
-
 // If true, QUIC respect HTTP2 SETTINGS frame rather than always close the
 // connection.
 bool FLAGS_quic_respect_http2_settings_frame = true;