message: Remove unnecessary sequence checker.
  Just use the task queue it represents instead.
  Also rename the accessor to not confuse it with the 'network thread'.
  Cr-Commit-Position: refs/heads/master@{#31375}
diff: @@ -264,7 +264,7 @@ class Call final : public webrtc::Call,
  void RegisterRateObserver();
  - rtc::TaskQueue* network_queue() const {
  + rtc::TaskQueue* send_transport_queue() const {
  return transport_send_ptr_->GetWorkerQueue();
  }
  @@ -277,7 +277,6 @@ class Call final : public webrtc::Call,
  const std::unique_ptr<CallStats> call_stats_;
  const std::unique_ptr<BitrateAllocator> bitrate_allocator_;
  Call::Config config_;
  - SequenceChecker network_sequence_checker_;
  NetworkState audio_network_state_;
  NetworkState video_network_state_;
  @@ -577,7 +576,6 @@ Call::Call(Clock* clock,
  RTC_DCHECK(config.event_log != nullptr);
  RTC_DCHECK(config.trials != nullptr);
  RTC_DCHECK(worker_thread_->IsCurrent());
  - network_sequence_checker_.Detach();
  call_stats_->RegisterStatsObserver(&receive_side_cc_);
  @@ -1033,14 +1031,6 @@ RtpTransportControllerSendInterface* Call::GetTransportControllerSend() {
  Call::Stats Call::GetStats() const {
  RTC_DCHECK_RUN_ON(worker_thread_);
  - // TODO(tommi): The following stats are managed on the process thread:
  - // - pacer_delay_ms (PacedSender::Process)
  - // - rtt_ms
  - // - recv_bandwidth_bps
  - // These are delivered on the network TQ:
  - // - send_bandwidth_bps (see OnTargetTransferRate)
  - // - max_padding_bitrate_bps (see OnAllocationLimitsChanged)
  -
  Stats stats;
  // TODO(srte): It is unclear if we only want to report queues if network is
  // available.
  @@ -1122,13 +1112,12 @@ void Call::OnSentPacket(const rtc::SentPacket& sent_packet) {
  }
  void Call::OnStartRateUpdate(DataRate start_rate) {
  - RTC_DCHECK(network_queue()->IsCurrent());
  + RTC_DCHECK_RUN_ON(send_transport_queue());
  bitrate_allocator_->UpdateStartRate(start_rate.bps<uint32_t>());
  }
  void Call::OnTargetTransferRate(TargetTransferRate msg) {
  - RTC_DCHECK(network_queue()->IsCurrent());
  - RTC_DCHECK_RUN_ON(&network_sequence_checker_);
  + RTC_DCHECK_RUN_ON(send_transport_queue());
  uint32_t target_bitrate_bps = msg.target_rate.bps();
  // For controlling the rate of feedback messages.
  @@ -1158,8 +1147,7 @@ void Call::OnTargetTransferRate(TargetTransferRate msg) {
  }
  void Call::OnAllocationLimitsChanged(BitrateAllocationLimits limits) {
  - RTC_DCHECK(network_queue()->IsCurrent());
  - RTC_DCHECK_RUN_ON(&network_sequence_checker_);
  + RTC_DCHECK_RUN_ON(send_transport_queue());
  transport_send_ptr_->SetAllocatedSendBitrateLimits(limits);
  @@ -1350,6 +1338,7 @@ PacketReceiver::DeliveryStatus Call::DeliverPacket(
  rtc::CopyOnWriteBuffer packet,
  int64_t packet_time_us) {
  RTC_DCHECK_RUN_ON(worker_thread_);
  +
  if (IsRtcp(packet.cdata(), packet.size()))
  return DeliverRtcp(media_type, packet.cdata(), packet.size());
  