gfe-relnote: (n/a) Deprecate --gfe2_reloadable_flag_quic_bbr2_avoid_unnecessary_probe_rtt.

PiperOrigin-RevId: 305282761
Change-Id: Ide60a8633ebf49966ee8f8c40b36484863bb2d2a

quic/core/congestion_control/bbr2_misc.h

diff --git a/quic/core/congestion_control/bbr2_misc.h b/quic/core/congestion_control/bbr2_misc.h
index 09b1f35..0c72131 100644
--- a/quic/core/congestion_control/bbr2_misc.h
+++ b/quic/core/congestion_control/bbr2_misc.h
@@ -176,8 +176,7 @@
       GetQuicReloadableFlag(quic_bbr2_add_ack_height_to_queueing_threshold);
 
   // Can be disabled by connection option 'B2RP'.
-  bool avoid_unnecessary_probe_rtt =
-      GetQuicReloadableFlag(quic_bbr2_avoid_unnecessary_probe_rtt);
+  bool avoid_unnecessary_probe_rtt = true;
 };
 
 class QUIC_EXPORT_PRIVATE RoundTripCounter {

quic/core/congestion_control/bbr2_sender.cc

diff --git a/quic/core/congestion_control/bbr2_sender.cc b/quic/core/congestion_control/bbr2_sender.cc
index 94cda02..ff5f74f 100644
--- a/quic/core/congestion_control/bbr2_sender.cc
+++ b/quic/core/congestion_control/bbr2_sender.cc
@@ -213,7 +213,6 @@
   last_sample_is_app_limited_ = congestion_event.last_sample_is_app_limited;
   if (congestion_event.bytes_in_flight == 0 &&
       params().avoid_unnecessary_probe_rtt) {
-    QUIC_RELOADABLE_FLAG_COUNT_N(quic_bbr2_avoid_unnecessary_probe_rtt, 2, 2);
     OnEnterQuiescence(event_time);
   }
 
@@ -308,7 +307,6 @@
                 << ", total_lost:" << model_.total_bytes_lost() << "  @ "
                 << sent_time;
   if (bytes_in_flight == 0 && params().avoid_unnecessary_probe_rtt) {
-    QUIC_RELOADABLE_FLAG_COUNT_N(quic_bbr2_avoid_unnecessary_probe_rtt, 1, 2);
     OnExitQuiescence(sent_time);
   }
   model_.OnPacketSent(sent_time, bytes_in_flight, packet_number, bytes,

quic/core/congestion_control/bbr2_simulator_test.cc

diff --git a/quic/core/congestion_control/bbr2_simulator_test.cc b/quic/core/congestion_control/bbr2_simulator_test.cc
index 949b283..e35915f 100644
--- a/quic/core/congestion_control/bbr2_simulator_test.cc
+++ b/quic/core/congestion_control/bbr2_simulator_test.cc
@@ -890,11 +890,8 @@
   sender_->OnPacketSent(SimulatedNow(), /*bytes_in_flight=*/0,
                         sender_unacked_map()->largest_sent_packet() + 1,
                         kDefaultMaxPacketSize, HAS_RETRANSMITTABLE_DATA);
-  if (GetQuicReloadableFlag(quic_bbr2_avoid_unnecessary_probe_rtt)) {
-    EXPECT_EQ(sender_->ExportDebugState().mode, Bbr2Mode::PROBE_BW);
-  } else {
-    EXPECT_EQ(sender_->ExportDebugState().mode, Bbr2Mode::PROBE_RTT);
-  }
+
+  EXPECT_EQ(sender_->ExportDebugState().mode, Bbr2Mode::PROBE_BW);
 }
 
 TEST_F(Bbr2DefaultTopologyTest, ProbeBwAfterQuiescencePostponeMinRttTimestamp) {
@@ -929,12 +926,9 @@
   SendBursts(params, 1, kDefaultTCPMSS, QuicTime::Delta::Zero());
   const QuicTime min_rtt_timestamp_after_idle =
       sender_->ExportDebugState().min_rtt_timestamp;
-  if (GetQuicReloadableFlag(quic_bbr2_avoid_unnecessary_probe_rtt)) {
-    EXPECT_LT(min_rtt_timestamp_before_idle + QuicTime::Delta::FromSeconds(14),
-              min_rtt_timestamp_after_idle);
-  } else {
-    EXPECT_EQ(min_rtt_timestamp_before_idle, min_rtt_timestamp_after_idle);
-  }
+
+  EXPECT_LT(min_rtt_timestamp_before_idle + QuicTime::Delta::FromSeconds(14),
+            min_rtt_timestamp_after_idle);
 }
 
 // Regression test for http://shortn/_Jt1QWtshAM.