Deprecate FLAGS_quic_reloadable_flag_quic_bbr_ack_spacing2 in the disabled position because it neve…

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 5220d3a94e31e49d701cb4a3a8bb9c02e13578b2..6207a12f8e444fe7742d88b04ae3669f5fcc1bef 100644
--- a/net/quic/core/congestion_control/bbr_sender.cc
+++ b/net/quic/core/congestion_control/bbr_sender.cc
@@ -80,9 +80,6 @@ BbrSender::BbrSender(const RttStats* rtt_stats,
       last_sent_packet_(0),
       current_round_trip_end_(0),
       max_bandwidth_(kBandwidthWindowSize, QuicBandwidth::Zero(), 0),
-      max_ack_spacing_(kBandwidthWindowSize, QuicTime::Delta::Zero(), 0),
-      largest_acked_time_(QuicTime::Zero()),
-      largest_acked_sent_time_(QuicTime::Zero()),
       max_ack_height_(kBandwidthWindowSize, 0, 0),
       aggregation_epoch_start_time_(QuicTime::Zero()),
       aggregation_epoch_bytes_(0),
@@ -250,10 +247,6 @@ void BbrSender::OnCongestionEvent(bool /*rtt_updated*/,
     min_rtt_expired = UpdateBandwidthAndMinRtt(event_time, acked_packets);
     UpdateRecoveryState(last_acked_packet, !lost_packets.empty(),
                         is_round_start);
-    if (FLAGS_quic_reloadable_flag_quic_bbr_ack_spacing2) {
-      QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_spacing2, 1, 2);
-      UpdateAckSpacing(event_time, last_acked_packet, acked_packets);
-    }
     if (FLAGS_quic_reloadable_flag_quic_bbr_ack_aggregation_bytes) {
       QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_aggregation_bytes, 1,
                         2);
@@ -527,42 +520,6 @@ void BbrSender::UpdateRecoveryState(QuicPacketNumber last_acked_packet,
   }
 }
 
-// TODO(ianswett): Move this logic into BandwidthSampler.
-void BbrSender::UpdateAckSpacing(QuicTime ack_time,
-                                 QuicPacketNumber largest_newly_acked,
-                                 const CongestionVector& acked_packets) {
-  // Ignore acks of reordered packets.
-  if (largest_newly_acked < unacked_packets_->largest_observed()) {
-    return;
-  }
-  // Ignore acks of only one packet to filter out delayed acks.
-  if (acked_packets.size() == 1) {
-    return;
-  }
-  QuicTime largest_newly_acked_sent_time =
-      unacked_packets_->GetTransmissionInfo(largest_newly_acked).sent_time;
-  // Initialize on the first ack.
-  if (!largest_acked_time_.IsInitialized()) {
-    largest_acked_time_ = ack_time;
-    largest_acked_sent_time_ = largest_newly_acked_sent_time;
-    return;
-  }
-  QuicTime::Delta ack_delta = ack_time - largest_acked_time_;
-  QuicTime::Delta send_delta =
-      largest_newly_acked_sent_time - largest_acked_sent_time_;
-  largest_acked_time_ = ack_time;
-  largest_acked_sent_time_ = largest_newly_acked_sent_time;
-  if (ack_delta <= send_delta) {
-    return;
-  }
-
-  // Limit the ack spacing to SRTT to filter outliers.
-  QuicTime::Delta ack_spacing =
-      std::min(ack_delta - send_delta, rtt_stats_->smoothed_rtt());
-  max_ack_spacing_.Update(ack_spacing, round_trip_count_);
-}
-
-// TODO(ianswett): Move this logic into BandwidthSampler.
 void BbrSender::UpdateAckAggregationBytes(QuicTime ack_time,
                                           QuicByteCount newly_acked_bytes) {
   // Compute how many bytes are expected to be delivered, assuming max bandwidth
@@ -619,11 +576,6 @@ void BbrSender::CalculateCongestionWindow(QuicByteCount bytes_acked) {
   if (rtt_variance_weight_ > 0.f && !BandwidthEstimate().IsZero()) {
     target_window += rtt_variance_weight_ * rtt_stats_->mean_deviation() *
                      BandwidthEstimate();
-  } else if (FLAGS_quic_reloadable_flag_quic_bbr_ack_spacing2 &&
-             is_at_full_bandwidth_) {
-    QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_spacing2, 2, 2);
-    // Add CWND for inter-ack spacing once STARTUP has been exited.
-    target_window += max_ack_spacing_.GetBest() * BandwidthEstimate();
   } else if (FLAGS_quic_reloadable_flag_quic_bbr_ack_aggregation_bytes &&
              is_at_full_bandwidth_) {
     QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_aggregation_bytes, 2,