Reland "Prepares PacingController for simplified packet queue."

This is a reland of acdc22d7845c5dde7c23366110e54e5d26127c85

Original change's description:
> Prepares PacingController for simplified packet queue.
>
> This CL removes references to RoundRobinPacketQueue::QueuedPacket,
> other than the method to release an RtpPacketToSend. It also moves
> both the BeginPop() and FinalizePop() to within a single helper
> method.
>
> A follow-up cleanup of the packet queue will stop exposing the
> QueuedPacket struct and replaces the the pop-methods with a single
> new one that just returns an RtpPacketToSend.
>
> Bug: webrtc:10809
> Change-Id: I5208a93e12e6b56714d483cc12d2a37225ea8e5e
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159889
> Commit-Queue: Erik Språng <sprang@webrtc.org>
> Reviewed-by: Philip Eliasson <philipel@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#29820}

TBR=philipel@webrtc.org

Bug: webrtc:10809
Change-Id: Id8196d9348d7fa69a5e410367b8a88e6039ef1b8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/160205
Commit-Queue: Erik Språng <sprang@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29867}

modules/pacing/pacing_controller.cc

@@ -99,6 +99,8 @@ PacingController::PacingController(Clock* clock,
       pace_audio_(!IsDisabled(*field_trials_, "WebRTC-Pacer-BlockAudio")),
       small_first_probe_packet_(
           IsEnabled(*field_trials_, "WebRTC-Pacer-SmallFirstProbePacket")),
+      send_side_bwe_with_overhead_(
+          IsEnabled(*field_trials_, "WebRTC-SendSideBwe-WithOverhead")),
       min_packet_limit_(kDefaultMinPacketLimit),
       last_timestamp_(clock_->CurrentTime()),
       paused_(false),
@@ -463,8 +465,10 @@ void PacingController::ProcessPackets() {
 
     // Fetch the next packet, so long as queue is not empty or budget is not
     // exhausted.
-    auto* packet = GetPendingPacket(pacing_info, target_send_time, now);
-    if (packet == nullptr) {
+    std::unique_ptr<RtpPacketToSend> rtp_packet =
+        GetPendingPacket(pacing_info, target_send_time, now);
+
+    if (rtp_packet == nullptr) {
       // No packet available to send, check if we should send padding.
       DataSize padding_to_add = PaddingToAdd(recommended_probe_size, data_sent);
       if (padding_to_add > DataSize::Zero()) {
@@ -485,14 +489,19 @@ void PacingController::ProcessPackets() {
       break;
     }
 
-    std::unique_ptr<RtpPacketToSend> rtp_packet = packet->ReleasePacket();
     RTC_DCHECK(rtp_packet);
+    RTC_DCHECK(rtp_packet->packet_type().has_value());
+    const RtpPacketToSend::Type packet_type = *rtp_packet->packet_type();
+    const DataSize packet_size = DataSize::bytes(
+        send_side_bwe_with_overhead_
+            ? rtp_packet->size()
+            : rtp_packet->payload_size() + rtp_packet->padding_size());
     packet_sender_->SendRtpPacket(std::move(rtp_packet), pacing_info);
 
-    data_sent += packet->size();
-    // Send succeeded, remove it from the queue and update send/process time to
-    // the target send time.
-    OnPacketSent(packet, target_send_time);
+    data_sent += packet_size;
+
+    // Send done, update send/process time to the target send time.
+    OnPacketSent(packet_type, packet_size, target_send_time);
     if (recommended_probe_size && data_sent > *recommended_probe_size)
       break;
 
@@ -551,7 +560,7 @@ DataSize PacingController::PaddingToAdd(
   return DataSize::Zero();
 }
 
-RoundRobinPacketQueue::QueuedPacket* PacingController::GetPendingPacket(
+std::unique_ptr<RtpPacketToSend> PacingController::GetPendingPacket(
     const PacedPacketInfo& pacing_info,
     Timestamp target_send_time,
     Timestamp now) {
@@ -593,23 +602,28 @@ RoundRobinPacketQueue::QueuedPacket* PacingController::GetPendingPacket(
     }
   }
 
-  return packet_queue_.BeginPop();
+  auto* queued_packet = packet_queue_.BeginPop();
+  std::unique_ptr<RtpPacketToSend> rtp_packet;
+  if (queued_packet != nullptr) {
+    rtp_packet = queued_packet->ReleasePacket();
+    packet_queue_.FinalizePop();
+  }
+  return rtp_packet;
 }
 
-void PacingController::OnPacketSent(RoundRobinPacketQueue::QueuedPacket* packet,
+void PacingController::OnPacketSent(RtpPacketToSend::Type packet_type,
+                                    DataSize packet_size,
                                     Timestamp send_time) {
   if (!first_sent_packet_time_) {
     first_sent_packet_time_ = send_time;
   }
-  bool audio_packet = packet->type() == RtpPacketToSend::Type::kAudio;
+  bool audio_packet = packet_type == RtpPacketToSend::Type::kAudio;
   if (!audio_packet || account_for_audio_) {
     // Update media bytes sent.
-    UpdateBudgetWithSentData(packet->size());
+    UpdateBudgetWithSentData(packet_size);
   }
   last_send_time_ = send_time;
   last_process_time_ = send_time;
-  // Send succeeded, remove it from the queue.
-  packet_queue_.FinalizePop();
 }
 
 void PacingController::OnPaddingSent(DataSize data_sent) {

modules/pacing/pacing_controller.h

@@ -150,11 +150,12 @@ class PacingController {
   DataSize PaddingToAdd(absl::optional<DataSize> recommended_probe_size,
                         DataSize data_sent) const;
 
-  RoundRobinPacketQueue::QueuedPacket* GetPendingPacket(
+  std::unique_ptr<RtpPacketToSend> GetPendingPacket(
       const PacedPacketInfo& pacing_info,
       Timestamp target_send_time,
       Timestamp now);
-  void OnPacketSent(RoundRobinPacketQueue::QueuedPacket* packet,
+  void OnPacketSent(RtpPacketToSend::Type packet_type,
+                    DataSize packet_size,
                     Timestamp send_time);
   void OnPaddingSent(DataSize padding_sent);
 
@@ -170,6 +171,7 @@ class PacingController {
   const bool send_padding_if_silent_;
   const bool pace_audio_;
   const bool small_first_probe_packet_;
+  const bool send_side_bwe_with_overhead_;
 
   TimeDelta min_packet_limit_;