Deprecate --gfe2_reloadable_flag_quic_copy_bbr_cwnd_to_bbr2.

PiperOrigin-RevId: 343865131
Change-Id: I3b7ccab4e00cac1e4b8004cf5508761d7e5d594d

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 6b93074..6cd3037 100644
--- a/quic/core/congestion_control/bbr2_sender.cc
+++ b/quic/core/congestion_control/bbr2_sender.cc
@@ -76,9 +76,8 @@
              /*pacing_gain=*/kInitialPacingGain,
              old_sender ? &old_sender->sampler_ : nullptr),
       initial_cwnd_(cwnd_limits().ApplyLimits(
-          (GetQuicReloadableFlag(quic_copy_bbr_cwnd_to_bbr2) && old_sender)
-              ? old_sender->GetCongestionWindow()
-              : (initial_cwnd_in_packets * kDefaultTCPMSS))),
+          (old_sender) ? old_sender->GetCongestionWindow()
+                       : (initial_cwnd_in_packets * kDefaultTCPMSS))),
       cwnd_(initial_cwnd_),
       pacing_rate_(kInitialPacingGain * QuicBandwidth::FromBytesAndTimeDelta(
                                             cwnd_,
@@ -88,10 +87,6 @@
       probe_bw_(this, &model_),
       probe_rtt_(this, &model_),
       last_sample_is_app_limited_(false) {
-  if (GetQuicReloadableFlag(quic_copy_bbr_cwnd_to_bbr2) && old_sender) {
-    QUIC_RELOADABLE_FLAG_COUNT(quic_copy_bbr_cwnd_to_bbr2);
-  }
-
   QUIC_DVLOG(2) << this << " Initializing Bbr2Sender. mode:" << mode_
                 << ", PacingRate:" << pacing_rate_ << ", Cwnd:" << cwnd_
                 << ", CwndLimits:" << cwnd_limits() << "  @ " << now;

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 f446ab5..c3362b3 100644
--- a/quic/core/congestion_control/bbr2_simulator_test.cc
+++ b/quic/core/congestion_control/bbr2_simulator_test.cc
@@ -1000,9 +1000,7 @@
   // Switch from |old_sender| to |sender_|.
   const QuicByteCount old_sender_cwnd = old_sender.GetCongestionWindow();
   sender_ = SetupBbr2Sender(&sender_endpoint_, &old_sender);
-  if (GetQuicReloadableFlag(quic_copy_bbr_cwnd_to_bbr2)) {
-    EXPECT_EQ(old_sender_cwnd, sender_->GetCongestionWindow());
-  }
+  EXPECT_EQ(old_sender_cwnd, sender_->GetCongestionWindow());
 
   // Send packets 5-7.
   now = now + QuicTime::Delta::FromMilliseconds(10);

quic/core/quic_flags_list.h

diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index 07e8712..bcf0ce6 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -24,7 +24,6 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_connection_set_initial_self_address, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_conservative_bursts, false)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_conservative_cwnd_and_pacing_gains, false)
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_copy_bbr_cwnd_to_bbr2, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_deallocate_message_right_after_sent, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_default_enable_5rto_blackhole_detection2, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_default_on_pto, false)