Deprecate --gfe2_reloadable_flag_quic_bbr2_use_post_inflight_to_detect_queuing.

PiperOrigin-RevId: 343865425
Change-Id: I875bfc5e8758e75124251e4ef3784fd140336a60

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 0b8991c..e91339f 100644
--- a/quic/core/congestion_control/bbr2_probe_bw.cc
+++ b/quic/core/congestion_control/bbr2_probe_bw.cc
@@ -126,6 +126,7 @@
   return Bbr2Mode::PROBE_BW;
 }
 
+// TODO(ianswett): Remove prior_in_flight from UpdateProbeDown.
 void Bbr2ProbeBwMode::UpdateProbeDown(
     QuicByteCount prior_in_flight,
     const Bbr2CongestionEvent& congestion_event) {
@@ -169,13 +170,8 @@
       << prior_in_flight << " congestion_event.bytes_in_flight:"
       << congestion_event.bytes_in_flight
       << ", inflight_with_headroom:" << inflight_with_headroom;
-  QuicByteCount bytes_in_flight = prior_in_flight;
-  if (GetQuicReloadableFlag(quic_bbr2_use_post_inflight_to_detect_queuing)) {
-    // TODO(ianswett): Remove prior_in_flight from UpdateProbeDown.
-    QUIC_RELOADABLE_FLAG_COUNT_N(quic_bbr2_use_post_inflight_to_detect_queuing,
-                                 2, 2);
-    bytes_in_flight = congestion_event.bytes_in_flight;
-  }
+  QuicByteCount bytes_in_flight = congestion_event.bytes_in_flight;
+
   if (bytes_in_flight > inflight_with_headroom) {
     // Stay in PROBE_DOWN.
     return;
@@ -450,13 +446,9 @@
     QuicByteCount queuing_threshold =
         (Params().probe_bw_probe_inflight_gain * bdp) +
         queuing_threshold_extra_bytes;
-    if (GetQuicReloadableFlag(quic_bbr2_use_post_inflight_to_detect_queuing)) {
-      QUIC_RELOADABLE_FLAG_COUNT_N(
-          quic_bbr2_use_post_inflight_to_detect_queuing, 1, 2);
-      is_queuing = congestion_event.bytes_in_flight >= queuing_threshold;
-    } else {
-      is_queuing = prior_in_flight >= queuing_threshold;
-    }
+
+    is_queuing = congestion_event.bytes_in_flight >= queuing_threshold;
+
     QUIC_DVLOG(3) << sender_
                   << " Checking if building up a queue. prior_in_flight:"
                   << prior_in_flight

quic/core/quic_flags_list.h

diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index bcf0ce6..e9b27fd 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -16,7 +16,6 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_bbr2_no_exit_startup_on_loss_with_bw_growth, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_bbr2_startup_loss_exit_use_max_delivered, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_bbr2_support_max_bootstrap_cwnd, true)
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_bbr2_use_post_inflight_to_detect_queuing, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_can_send_ack_frequency, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_check_keys_before_writing, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_clean_up_spdy_session_destructor, true)