Implement a QUIC No PRR connection option, NPRR. Protected by FLAGS_quic_allow_no_prr

net/quic/congestion_control/pacing_sender.cc

Index: net/quic/congestion_control/pacing_sender.cc
diff --git a/net/quic/congestion_control/pacing_sender.cc b/net/quic/congestion_control/pacing_sender.cc
index 76cd2141adc1483d8f5bca651a542591e95fe041..34acbf3e71bae07824c92958b8844c8a0a473081 100644
--- a/net/quic/congestion_control/pacing_sender.cc
+++ b/net/quic/congestion_control/pacing_sender.cc
@@ -53,6 +53,10 @@ void PacingSender::OnCongestionEvent(bool rtt_updated,
                                      QuicByteCount bytes_in_flight,
                                      const CongestionVector& acked_packets,
                                      const CongestionVector& lost_packets) {
+  if (FLAGS_quic_allow_noprr && !lost_packets.empty()) {
+    // Clear any burst tokens when entering recovery.
+    burst_tokens_ = 0;
+  }
   sender_->OnCongestionEvent(rtt_updated, bytes_in_flight, acked_packets,
                              lost_packets);
 }