Enable Kathleen Nichols min rtt algorithm with a 1 minute window in

net/quic/quic_sent_packet_manager.cc

Index: net/quic/quic_sent_packet_manager.cc
diff --git a/net/quic/quic_sent_packet_manager.cc b/net/quic/quic_sent_packet_manager.cc
index 15f0ad96ed039cbf612b08d539acc7c7fa414b9a..5ca809d532a92d335abcaf5de7be827a7365bfd5 100644
--- a/net/quic/quic_sent_packet_manager.cc
+++ b/net/quic/quic_sent_packet_manager.cc
@@ -20,6 +20,11 @@ using std::max;
 using std::min;
 
 namespace net {
+
+// The length of the recent min rtt window in seconds. Windowing is disabled for
+// values less than or equal to 0.
+int32 FLAGS_quic_recent_min_rtt_window_s = 60;
+
 namespace {
 static const int kDefaultRetransmissionTimeMs = 500;
 // TCP RFC calls for 1 second RTO however Linux differs from this default and
@@ -44,6 +49,8 @@ static const size_t kNumMinRttSamplesAfterQuiescence = 2;
 // Number of unpaced packets to send after quiescence.
 static const size_t kInitialUnpacedBurst = 10;
 
+// Use a 1 minute window for Recent Min RTT with BBR.
+
 bool HasCryptoHandshake(const TransmissionInfo& transmission_info) {
   if (transmission_info.retransmittable_frames == NULL) {
     return false;
@@ -91,6 +98,10 @@ void QuicSentPacketManager::SetFromConfig(const QuicConfig& config) {
   // TODO(ianswett): BBR is currently a server only feature.
   if (config.HasReceivedConnectionOptions() &&
       ContainsQuicTag(config.ReceivedConnectionOptions(), kTBBR)) {
+    if (FLAGS_quic_recent_min_rtt_window_s > 0) {
+      rtt_stats_.set_recent_min_rtt_window(
+          QuicTime::Delta::FromSeconds(FLAGS_quic_recent_min_rtt_window_s));
+    }
     send_algorithm_.reset(
         SendAlgorithmInterface::Create(clock_, &rtt_stats_, kTCPBBR, stats_));
   }