deprecate FLAGS_quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate in disabled state.

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 0c2104b5bd190c9e415d7d47460a44227d27c47b..b466337486965aa0fb6b82b0747cfc202eeb0f3b 100644
--- a/net/quic/core/congestion_control/bbr_sender.cc
+++ b/net/quic/core/congestion_control/bbr_sender.cc
@@ -192,16 +192,6 @@ QuicBandwidth BbrSender::PacingRate(QuicByteCount bytes_in_flight) const {
     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);
-    if (pacing_gain_ > 1) {
-      return max_bandwidth_.GetBest();
-    } else {
-      return max_bandwidth_.GetThirdBest();
-    }
-  }
   return pacing_rate_;
 }
 
@@ -218,15 +208,6 @@ 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 && pacing_gain_ >= 1) {
-    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_;
 }