Remove |running_| state from NackModule to avoid running a tight loop.

webrtc/modules/video_coding/nack_module.h

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 18 matching lines @@
 class NackModule : public Module {
  public:
   NackModule(Clock* clock,
              NackSender* nack_sender,
              KeyFrameRequestSender* keyframe_request_sender);
 
   int OnReceivedPacket(const VCMPacket& packet);
   void ClearUpTo(uint16_t seq_num);
   void UpdateRtt(int64_t rtt_ms);
   void Clear();
-  void Stop();
 
   // Module implementation
   int64_t TimeUntilNextProcess() override;
   void Process() override;
 
  private:
   // Which fields to consider when deciding which packet to nack in
   // GetNackBatch.
   enum NackFilterOptions { kSeqNumOnly, kTimeOnly, kSeqNumAndTime };
 
@@ skipping 25 matching lines @@
   // Returns how many packets we have to wait in order to receive the packet
   // with probability |probabilty| or higher.
   int WaitNumberOfPackets(float probability) const
       EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   rtc::CriticalSection crit_;
   Clock* const clock_;
   NackSender* const nack_sender_;
   KeyFrameRequestSender* const keyframe_request_sender_;
 
+  // TODO(philipel): Some of the variables below are consistently used on a
+  // known thread (e.g. see |initialized_|). Those probably do not need
+  // synchronized access.
   std::map<uint16_t, NackInfo, DescendingSeqNumComp<uint16_t>> nack_list_
       GUARDED_BY(crit_);
   std::set<uint16_t, DescendingSeqNumComp<uint16_t>> keyframe_list_
       GUARDED_BY(crit_);
   video_coding::Histogram reordering_histogram_ GUARDED_BY(crit_);
-  bool running_ GUARDED_BY(crit_);
   bool initialized_ GUARDED_BY(crit_);
   int64_t rtt_ms_ GUARDED_BY(crit_);
   uint16_t newest_seq_num_ GUARDED_BY(crit_);
-  int64_t next_process_time_ms_ GUARDED_BY(crit_);
+
+  // Only touched on the process thread.
+  int64_t next_process_time_ms_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_NACK_MODULE_H_