Simplify QUIC stateless rejects by latching the value of FLAGS_enable_quic_stateless_reject_support…

net/quic/quic_crypto_server_stream.cc

Index: net/quic/quic_crypto_server_stream.cc
diff --git a/net/quic/quic_crypto_server_stream.cc b/net/quic/quic_crypto_server_stream.cc
index b7c72c81c0fd2522145b3f9bf5a015b0ef88002d..30ba1585704067694ffea6dae2a71a5d963cf9d5 100644
--- a/net/quic/quic_crypto_server_stream.cc
+++ b/net/quic/quic_crypto_server_stream.cc
@@ -38,7 +38,8 @@ QuicCryptoServerStream::QuicCryptoServerStream(
       num_handshake_messages_(0),
       num_handshake_messages_with_server_nonces_(0),
       num_server_config_update_messages_sent_(0),
-      use_stateless_rejects_if_peer_supported_(false),
+      use_stateless_rejects_if_peer_supported_(
+          FLAGS_enable_quic_stateless_reject_support),
       peer_supports_stateless_rejects_(false) {
   DCHECK_EQ(Perspective::IS_SERVER, session->connection()->perspective());
 }
@@ -93,7 +94,7 @@ void QuicCryptoServerStream::FinishProcessingHandshakeMessage(
   DCHECK(validate_client_hello_cb_ != nullptr);
   validate_client_hello_cb_ = nullptr;
 
-  if (FLAGS_enable_quic_stateless_reject_support) {
+  if (use_stateless_rejects_if_peer_supported_) {
     peer_supports_stateless_rejects_ = DoesPeerSupportStatelessRejects(message);
   }
 
@@ -108,8 +109,9 @@ void QuicCryptoServerStream::FinishProcessingHandshakeMessage(
   }
 
   if (reply.tag() != kSHLO) {
-    if (FLAGS_enable_quic_stateless_reject_support &&
-        reply.tag() == kSREJ) {
+    if (reply.tag() == kSREJ) {
+      DCHECK(use_stateless_rejects_if_peer_supported());
+      DCHECK(peer_supports_stateless_rejects());
       // Before sending the SREJ, cause the connection to save crypto packets
       // so that they can be added to the time wait list manager and
       // retransmitted.
@@ -117,7 +119,7 @@ void QuicCryptoServerStream::FinishProcessingHandshakeMessage(
     }
     SendHandshakeMessage(reply);
 
-    if (FLAGS_enable_quic_stateless_reject_support && reply.tag() == kSREJ) {
+    if (reply.tag() == kSREJ) {
       DCHECK(use_stateless_rejects_if_peer_supported());
       DCHECK(peer_supports_stateless_rejects());
       DCHECK(!handshake_confirmed());
@@ -262,7 +264,6 @@ QuicErrorCode QuicCryptoServerStream::ProcessClientHello(
   previous_source_address_tokens_ = result.info.source_address_tokens;
 
   const bool use_stateless_rejects_in_crypto_config =
-      FLAGS_enable_quic_stateless_reject_support &&
       use_stateless_rejects_if_peer_supported_ &&
       peer_supports_stateless_rejects_;
   QuicConnection* connection = session()->connection();