Add a new flag to require QUIC handshake confirmation, but only for versions before 33 FLAGS_quic_r…

net/quic/crypto/quic_crypto_server_config.cc

Index: net/quic/crypto/quic_crypto_server_config.cc
diff --git a/net/quic/crypto/quic_crypto_server_config.cc b/net/quic/crypto/quic_crypto_server_config.cc
index a26088d2d18160779d743dd2519518de4869a65d..38fddd0489c324686489e7b26cc72cf7370732b3 100644
--- a/net/quic/crypto/quic_crypto_server_config.cc
+++ b/net/quic/crypto/quic_crypto_server_config.cc
@@ -1219,7 +1219,8 @@ void QuicCryptoServerConfig::EvaluateClientHelloAfterGetProof(
   // If we hit this block, the server nonce was empty.  If we're requiring
   // handshake confirmation for DoS reasons and there's no server nonce present,
   // reject the CHLO.
-  if (FLAGS_quic_require_handshake_confirmation) {
+  if (FLAGS_quic_require_handshake_confirmation ||
+      FLAGS_quic_require_handshake_confirmation_pre33) {
     info->reject_reasons.push_back(SERVER_NONCE_REQUIRED_FAILURE);
     helper.ValidationComplete(QUIC_NO_ERROR, "");
     return;