Add QUIC code counters to observe the effect of application driven pacing.

PiperOrigin-RevId: 684890626

quiche/quic/core/congestion_control/bbr2_misc.cc

diff --git a/quiche/quic/core/congestion_control/bbr2_misc.cc b/quiche/quic/core/congestion_control/bbr2_misc.cc
index 00879b9..1e64682 100644
--- a/quiche/quic/core/congestion_control/bbr2_misc.cc
+++ b/quiche/quic/core/congestion_control/bbr2_misc.cc
@@ -231,6 +231,11 @@
         // pacing rate when congestion_event.bytes_lost > 0. The idea is to
         // avoid going over what the application needs at the earliest signs of
         // network congestion.
+        if (application_bandwidth_target_ < bandwidth_lo_) {
+          QUIC_CODE_COUNT(quic_bbr2_app_driven_pacing_in_effect);
+        } else {
+          QUIC_CODE_COUNT(quic_bbr2_app_driven_pacing_no_effect);
+        }
         bandwidth_lo_ = std::min(application_bandwidth_target_, bandwidth_lo_);
         QUIC_DVLOG(3) << "bandwidth_lo_ updated to " << bandwidth_lo_
                       << "after applying application_driven_pacing at "

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 6118546..21134ac 100644
--- a/quiche/quic/core/congestion_control/bbr2_sender.cc
+++ b/quiche/quic/core/congestion_control/bbr2_sender.cc
@@ -278,6 +278,7 @@
 
 void Bbr2Sender::SetApplicationDrivenPacingRate(
     QuicBandwidth application_bandwidth_target) {
+  QUIC_CODE_COUNT(quic_bbr2_set_app_driven_pacing_rate);
   model_.SetApplicationBandwidthTarget(application_bandwidth_target);
 }
 

quiche/quic/core/quic_connection.cc

diff --git a/quiche/quic/core/quic_connection.cc b/quiche/quic/core/quic_connection.cc
index 67f337d..f069d85 100644
--- a/quiche/quic/core/quic_connection.cc
+++ b/quiche/quic/core/quic_connection.cc
@@ -681,6 +681,7 @@
 
 void QuicConnection::SetApplicationDrivenPacingRate(
     QuicBandwidth application_driven_pacing_rate) {
+  QUIC_CODE_COUNT(quic_connection_set_app_driven_pacing_rate);
   sent_packet_manager_.SetApplicationDrivenPacingRate(
       application_driven_pacing_rate);
 }