Deprecate --quic_bbr2_support_new_startup_pacing_gain.

PiperOrigin-RevId: 469192491

quiche/quic/core/congestion_control/bbr2_sender.cc

diff --git a/quiche/quic/core/congestion_control/bbr2_sender.cc b/quiche/quic/core/congestion_control/bbr2_sender.cc
index c6fab64..208858b 100644
--- a/quiche/quic/core/congestion_control/bbr2_sender.cc
+++ b/quiche/quic/core/congestion_control/bbr2_sender.cc
@@ -127,10 +127,7 @@
     QUIC_RELOADABLE_FLAG_COUNT_N(quic_bbr2_extra_acked_window, 2, 2);
     model_.SetMaxAckHeightTrackerWindowLength(40);
   }
-  if (GetQuicReloadableFlag(quic_bbr2_support_new_startup_pacing_gain) &&
-      ContainsQuicTag(connection_options, kBBQ1)) {
-    QUIC_RELOADABLE_FLAG_COUNT_N(quic_bbr2_support_new_startup_pacing_gain, 2,
-                                 2);
+  if (ContainsQuicTag(connection_options, kBBQ1)) {
     params_.startup_pacing_gain = 2.773;
     params_.drain_pacing_gain = 1.0 / params_.drain_cwnd_gain;
   }

quiche/quic/core/congestion_control/bbr2_simulator_test.cc

diff --git a/quiche/quic/core/congestion_control/bbr2_simulator_test.cc b/quiche/quic/core/congestion_control/bbr2_simulator_test.cc
index 43645e3..d4ee77d 100644
--- a/quiche/quic/core/congestion_control/bbr2_simulator_test.cc
+++ b/quiche/quic/core/congestion_control/bbr2_simulator_test.cc
@@ -618,7 +618,6 @@
 }
 
 TEST_F(Bbr2DefaultTopologyTest, SimpleTransferBBQ1) {
-  SetQuicReloadableFlag(quic_bbr2_support_new_startup_pacing_gain, true);
   SetConnectionOption(kBBQ1);
   DefaultTopologyParams params;
   CreateNetwork(params);

quiche/quic/core/congestion_control/bbr_sender.cc

diff --git a/quiche/quic/core/congestion_control/bbr_sender.cc b/quiche/quic/core/congestion_control/bbr_sender.cc
index 99b6a04..756f32c 100644
--- a/quiche/quic/core/congestion_control/bbr_sender.cc
+++ b/quiche/quic/core/congestion_control/bbr_sender.cc
@@ -230,13 +230,7 @@
   if (config.HasClientRequestedIndependentOption(kBBQ1, perspective)) {
     set_high_gain(kDerivedHighGain);
     set_high_cwnd_gain(kDerivedHighGain);
-    if (GetQuicReloadableFlag(quic_bbr2_support_new_startup_pacing_gain)) {
-      QUIC_RELOADABLE_FLAG_COUNT_N(quic_bbr2_support_new_startup_pacing_gain, 1,
-                                   2);
-      set_drain_gain(1.0 / kDerivedHighCWNDGain);
-    } else {
-      set_drain_gain(1.f / kDerivedHighGain);
-    }
+    set_drain_gain(1.0 / kDerivedHighCWNDGain);
   }
   if (config.HasClientRequestedIndependentOption(kBBQ3, perspective)) {
     enable_ack_aggregation_during_startup_ = true;

quiche/quic/core/quic_flags_list.h

diff --git a/quiche/quic/core/quic_flags_list.h b/quiche/quic/core/quic_flags_list.h
index 46573ec..607a8fc 100644
--- a/quiche/quic/core/quic_flags_list.h
+++ b/quiche/quic/core/quic_flags_list.h
@@ -19,8 +19,6 @@
 QUIC_FLAG(quic_reloadable_flag_quic_bbr2_no_probe_up_exit_if_no_queue, true)
 // If trrue, early return before write control frame in OnCanWrite() if the connection is already closed.
 QUIC_FLAG(quic_reloadable_flag_quic_no_write_control_frame_upon_connection_close, true)
-// If true and BBQ1 connection option is set, QUIC BBR will use a pacing gain of 2.773 at startup and 0.5 at DRAIN.
-QUIC_FLAG(quic_reloadable_flag_quic_bbr2_support_new_startup_pacing_gain, true)
 // If true, 1) remove all experiments that tunes blackhole detection delay or path degrading delay, and 2) ensure network blackhole delay is at least path degrading delay plus 2 PTOs.
 QUIC_FLAG(quic_reloadable_flag_quic_remove_blackhole_detection_experiments, true)
 // If true, QUIC Legacy Version Encapsulation will be disabled.