Remain in packet conservation mode if BBR is in PROBE_BW and not in high-gain mode. Protected by F…

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 666a9d7f62997bfc452ec7bb7a972cf50139ed2d..4c025330cbad6ace2c3ff49afb79ab8d9ef02b22 100644
--- a/net/quic/core/congestion_control/bbr_sender.cc
+++ b/net/quic/core/congestion_control/bbr_sender.cc
@@ -515,6 +515,25 @@ void BbrSender::UpdateRecoveryState(QuicPacketNumber last_acked_packet,
       // Exit recovery if appropriate.
       if (!has_losses && last_acked_packet > end_recovery_at_) {
         recovery_state_ = NOT_IN_RECOVERY;
+        return;
+      }
+
+      if (!FLAGS_quic_reloadable_flag_quic_bbr_extra_conservation) {
+        return;
+      }
+
+      // Use "single round in conservation" approach outside of PROBE_BW.
+      if (mode_ != PROBE_BW) {
+        return;
+      }
+
+      // Switch between conservation and growth depending on position in the
+      // gain cycle.
+      if (cycle_current_offset_ == 0 ||
+          cycle_current_offset_ == kGainCycleLength - 1) {
+        recovery_state_ = GROWTH;
+      } else {
+        recovery_state_ = CONSERVATION;
       }
       break;
   }