gfe-relnote: (n/a) Deprecate --gfe2_reloadable_flag_quic_bbr2_exit_probe_bw_down_after_one_rtt.

PiperOrigin-RevId: 291723865
Change-Id: I6837ee2e27149e454610026684c4150c375ba2d6

quic/core/congestion_control/bbr2_probe_bw.cc

diff --git a/quic/core/congestion_control/bbr2_probe_bw.cc b/quic/core/congestion_control/bbr2_probe_bw.cc
index 3c8c787..e1cb58b 100644
--- a/quic/core/congestion_control/bbr2_probe_bw.cc
+++ b/quic/core/congestion_control/bbr2_probe_bw.cc
@@ -232,20 +232,11 @@
 // long, as seen in some multi-sender simulator tests.
 bool Bbr2ProbeBwMode::HasStayedLongEnoughInProbeDown(
     const Bbr2CongestionEvent& congestion_event) const {
-  if (exit_probe_down_after_one_rtt_) {
-    QUIC_RELOADABLE_FLAG_COUNT(quic_bbr2_exit_probe_bw_down_after_one_rtt);
-    // Stay in PROBE_DOWN for at most the time of a min rtt, as it is done in
-    // BBRv1. The intention here is to figure out whether the performance
-    // regression in BBRv2 is because it stays in PROBE_DOWN for too long.
-    // TODO(wub): Consider exit after a full round instead, which typically
-    // indicates most(if not all) packets sent during PROBE_UP have been acked.
-    return HasPhaseLasted(model_->MinRtt(), congestion_event);
-  }
-  // The amount of time to stay in PROBE_DOWN, as a fraction of probe wait time.
-  const double kProbeWaitFraction = 0.2;
-  return HasCycleLasted(cycle_.probe_wait_time * kProbeWaitFraction,
-                        congestion_event) ||
-         IsTimeToProbeForRenoCoexistence(kProbeWaitFraction, congestion_event);
+  // Stay in PROBE_DOWN for at most the time of a min rtt, as it is done in
+  // BBRv1.
+  // TODO(wub): Consider exit after a full round instead, which typically
+  // indicates most(if not all) packets sent during PROBE_UP have been acked.
+  return HasPhaseLasted(model_->MinRtt(), congestion_event);
 }
 
 bool Bbr2ProbeBwMode::HasCycleLasted(

quic/core/congestion_control/bbr2_probe_bw.h

diff --git a/quic/core/congestion_control/bbr2_probe_bw.h b/quic/core/congestion_control/bbr2_probe_bw.h
index 45b5a73..9f2f142 100644
--- a/quic/core/congestion_control/bbr2_probe_bw.h
+++ b/quic/core/congestion_control/bbr2_probe_bw.h
@@ -122,10 +122,6 @@
 
   bool last_cycle_probed_too_high_;
   bool last_cycle_stopped_risky_probe_;
-
-  // Latched value of --quic_bbr2_exit_probe_bw_down_after_one_rtt.
-  const bool exit_probe_down_after_one_rtt_ =
-      GetQuicReloadableFlag(quic_bbr2_exit_probe_bw_down_after_one_rtt);
 };
 
 QUIC_EXPORT_PRIVATE std::ostream& operator<<(