Add a new BDP method on QUIC BBRv2 that doesn't take any arguments and always uses MaxBandwidth() and use it where MaxBandwidth() is being used.  No functional change, not flag protected.

PiperOrigin-RevId: 345018169
Change-Id: Idfefa6d595ece3322c8743c4f59b5f06e347a127

quic/core/congestion_control/bbr2_drain.cc

diff --git a/quic/core/congestion_control/bbr2_drain.cc b/quic/core/congestion_control/bbr2_drain.cc
index 6022639..924127b 100644
--- a/quic/core/congestion_control/bbr2_drain.cc
+++ b/quic/core/congestion_control/bbr2_drain.cc
@@ -25,22 +25,21 @@
   if (congestion_event.bytes_in_flight <= drain_target) {
     QUIC_DVLOG(3) << sender_ << " Exiting DRAIN. bytes_in_flight:"
                   << congestion_event.bytes_in_flight
-                  << ", bdp:" << model_->BDP(model_->MaxBandwidth())
+                  << ", bdp:" << model_->BDP()
                   << ", drain_target:" << drain_target << "  @ "
                   << congestion_event.event_time;
     return Bbr2Mode::PROBE_BW;
   }
 
   QUIC_DVLOG(3) << sender_ << " Staying in DRAIN. bytes_in_flight:"
-                << congestion_event.bytes_in_flight
-                << ", bdp:" << model_->BDP(model_->MaxBandwidth())
+                << congestion_event.bytes_in_flight << ", bdp:" << model_->BDP()
                 << ", drain_target:" << drain_target << "  @ "
                 << congestion_event.event_time;
   return Bbr2Mode::DRAIN;
 }
 
 QuicByteCount Bbr2DrainMode::DrainTarget() const {
-  QuicByteCount bdp = model_->BDP(model_->MaxBandwidth());
+  QuicByteCount bdp = model_->BDP();
   return std::max<QuicByteCount>(bdp, sender_->GetMinimumCongestionWindow());
 }
 

quic/core/congestion_control/bbr2_misc.h

diff --git a/quic/core/congestion_control/bbr2_misc.h b/quic/core/congestion_control/bbr2_misc.h
index 5cf0579..2134bd6 100644
--- a/quic/core/congestion_control/bbr2_misc.h
+++ b/quic/core/congestion_control/bbr2_misc.h
@@ -345,6 +345,9 @@
 
   void OnApplicationLimited() { bandwidth_sampler_.OnAppLimited(); }
 
+  // Calculates BDP using the current MaxBandwidth.
+  QuicByteCount BDP() const { return BDP(MaxBandwidth()); }
+
   QuicByteCount BDP(QuicBandwidth bandwidth) const {
     return bandwidth * MinRtt();
   }

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 f76b5f4..1b01d9d 100644
--- a/quic/core/congestion_control/bbr2_probe_bw.cc
+++ b/quic/core/congestion_control/bbr2_probe_bw.cc
@@ -178,7 +178,7 @@
   }
 
   // Transition to PROBE_CRUISE iff we've drained to target.
-  QuicByteCount bdp = model_->BDP(model_->MaxBandwidth());
+  QuicByteCount bdp = model_->BDP();
   QUIC_DVLOG(3) << sender_ << " Checking if drained to target. bytes_in_flight:"
                 << bytes_in_flight << ", bdp:" << bdp;
   if (bytes_in_flight < bdp) {
@@ -450,7 +450,7 @@
     // TCP uses min_rtt instead of a full round:
     //   HasPhaseLasted(model_->MinRtt(), congestion_event)
   } else if (cycle_.rounds_in_phase > 0) {
-    const QuicByteCount bdp = model_->BDP(model_->MaxBandwidth());
+    const QuicByteCount bdp = model_->BDP();
     QuicByteCount queuing_threshold_extra_bytes = 2 * kDefaultTCPMSS;
     if (Params().add_ack_height_to_queueing_threshold) {
       queuing_threshold_extra_bytes += model_->MaxAckHeight();

quic/core/congestion_control/bbr2_startup.cc

diff --git a/quic/core/congestion_control/bbr2_startup.cc b/quic/core/congestion_control/bbr2_startup.cc
index 5c47adb..eb0dc08 100644
--- a/quic/core/congestion_control/bbr2_startup.cc
+++ b/quic/core/congestion_control/bbr2_startup.cc
@@ -107,7 +107,7 @@
   // At the end of a round trip. Check if loss is too high in this round.
   if (model_->IsInflightTooHigh(congestion_event,
                                 Params().startup_full_loss_count)) {
-    QuicByteCount new_inflight_hi = model_->BDP(model_->MaxBandwidth());
+    QuicByteCount new_inflight_hi = model_->BDP();
     if (Params().startup_loss_exit_use_max_delivered_for_inflight_hi) {
       if (new_inflight_hi < model_->max_bytes_delivered_in_round()) {
         QUIC_RELOADABLE_FLAG_COUNT_N(