Continue sending at the max bandwidth measured in the last two rounds for another SRTT. Protected …

net/quic/core/congestion_control/bbr_sender.cc

Index: net/quic/core/congestion_control/bbr_sender.cc
diff --git a/net/quic/core/congestion_control/bbr_sender.cc b/net/quic/core/congestion_control/bbr_sender.cc
index 623cfb78337ba35687af39a48cccec3a37ad2e64..d02ab68e1e2b4388d7506fa41465deab59ce56ad 100644
--- a/net/quic/core/congestion_control/bbr_sender.cc
+++ b/net/quic/core/congestion_control/bbr_sender.cc
@@ -145,11 +145,17 @@ QuicTime::Delta BbrSender::TimeUntilSend(QuicTime /* now */,
   return QuicTime::Delta::Infinite();
 }
 
-QuicBandwidth BbrSender::PacingRate(QuicByteCount /*bytes_in_flight*/) const {
+QuicBandwidth BbrSender::PacingRate(QuicByteCount bytes_in_flight) const {
   if (pacing_rate_.IsZero()) {
     return kHighGain * QuicBandwidth::FromBytesAndTimeDelta(
                            initial_congestion_window_, GetMinRtt());
   }
+  if (FLAGS_quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate &&
+      mode_ == PROBE_BW && bytes_in_flight > congestion_window_) {
+    QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate,
+                      1, 2);
+    return max_bandwidth_.GetThirdBest();
+  }
   return pacing_rate_;
 }
 
@@ -166,6 +172,15 @@ QuicByteCount BbrSender::GetCongestionWindow() const {
     return std::min(congestion_window_, recovery_window_);
   }
 
+  if (FLAGS_quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate &&
+      mode_ == PROBE_BW) {
+    QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate,
+                      2, 2);
+    // Send for another SRTT at a more recently measured bandwidth.
+    return congestion_window_ +
+           max_bandwidth_.GetThirdBest() * rtt_stats_->smoothed_rtt();
+  }
+
   return congestion_window_;
 }