Add a --quic_allow_chlo_buffering flag. Default value is true, no behavior change.

net/tools/quic/quic_dispatcher.cc

Index: net/tools/quic/quic_dispatcher.cc
diff --git a/net/tools/quic/quic_dispatcher.cc b/net/tools/quic/quic_dispatcher.cc
index 8b3ed42121950622df140a0bd918e1273bfe8175..9c87544bfd9aec78884e9167fb10cb773d624cf2 100644
--- a/net/tools/quic/quic_dispatcher.cc
+++ b/net/tools/quic/quic_dispatcher.cc
@@ -719,8 +719,8 @@ void QuicDispatcher::ProcessChlo() {
       !ShouldCreateOrBufferPacketForConnection(current_connection_id_)) {
     return;
   }
-
-  if (FLAGS_quic_limit_num_new_sessions_per_epoll_loop &&
+  if (FLAGS_quic_allow_chlo_buffering &&
+      FLAGS_quic_limit_num_new_sessions_per_epoll_loop &&
       new_sessions_allowed_per_event_loop_ <= 0) {
     // Can't create new session any more. Wait till next event loop.
     if (!buffered_packets_.HasChloForConnection(current_connection_id_)) {
@@ -828,11 +828,13 @@ class StatelessRejectorProcessDoneCallback
 void QuicDispatcher::MaybeRejectStatelessly(QuicConnectionId connection_id,
                                             const QuicPacketHeader& header) {
   // TODO(rch): This logic should probably live completely inside the rejector.
-  if (!FLAGS_quic_use_cheap_stateless_rejects ||
+  if (!FLAGS_quic_allow_chlo_buffering ||
+      !FLAGS_quic_use_cheap_stateless_rejects ||
       !FLAGS_enable_quic_stateless_reject_support ||
       !ShouldAttemptCheapStatelessRejection()) {
     // Not use cheap stateless reject.
-    if (!ChloExtractor::Extract(*current_packet_, GetSupportedVersions(),
+    if (FLAGS_quic_allow_chlo_buffering &&
+        !ChloExtractor::Extract(*current_packet_, GetSupportedVersions(),
                                 nullptr)) {
       // Buffer non-CHLO packets.
       ProcessUnauthenticatedHeaderFate(kFateBuffer, connection_id,