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diff --git a/third_party/libwebrtc/modules/video_coding/nack_requester.h b/third_party/libwebrtc/modules/video_coding/nack_requester.h
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index 0000000000..c860787dcf
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+++ b/third_party/libwebrtc/modules/video_coding/nack_requester.h
@@ -0,0 +1,157 @@
+/*
+ *  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.
+ */
+
+#ifndef MODULES_VIDEO_CODING_NACK_REQUESTER_H_
+#define MODULES_VIDEO_CODING_NACK_REQUESTER_H_
+
+#include <stdint.h>
+
+#include <map>
+#include <set>
+#include <vector>
+
+#include "api/field_trials_view.h"
+#include "api/sequence_checker.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/units/time_delta.h"
+#include "api/units/timestamp.h"
+#include "modules/include/module_common_types.h"
+#include "modules/video_coding/histogram.h"
+#include "rtc_base/numerics/sequence_number_util.h"
+#include "rtc_base/task_utils/repeating_task.h"
+#include "rtc_base/thread_annotations.h"
+#include "system_wrappers/include/clock.h"
+
+namespace webrtc {
+
+class NackRequesterBase {
+ public:
+  virtual ~NackRequesterBase() = default;
+  virtual void ProcessNacks() = 0;
+};
+
+class NackPeriodicProcessor {
+ public:
+  static constexpr TimeDelta kUpdateInterval = TimeDelta::Millis(20);
+  explicit NackPeriodicProcessor(TimeDelta update_interval = kUpdateInterval);
+  ~NackPeriodicProcessor();
+  void RegisterNackModule(NackRequesterBase* module);
+  void UnregisterNackModule(NackRequesterBase* module);
+
+ private:
+  void ProcessNackModules() RTC_RUN_ON(sequence_);
+
+  const TimeDelta update_interval_;
+  RepeatingTaskHandle repeating_task_ RTC_GUARDED_BY(sequence_);
+  std::vector<NackRequesterBase*> modules_ RTC_GUARDED_BY(sequence_);
+  RTC_NO_UNIQUE_ADDRESS SequenceChecker sequence_;
+};
+
+class ScopedNackPeriodicProcessorRegistration {
+ public:
+  ScopedNackPeriodicProcessorRegistration(NackRequesterBase* module,
+                                          NackPeriodicProcessor* processor);
+  ~ScopedNackPeriodicProcessorRegistration();
+
+ private:
+  NackRequesterBase* const module_;
+  NackPeriodicProcessor* const processor_;
+};
+
+class NackRequester final : public NackRequesterBase {
+ public:
+  NackRequester(TaskQueueBase* current_queue,
+                NackPeriodicProcessor* periodic_processor,
+                Clock* clock,
+                NackSender* nack_sender,
+                KeyFrameRequestSender* keyframe_request_sender,
+                const FieldTrialsView& field_trials);
+  ~NackRequester();
+
+  void ProcessNacks() override;
+
+  int OnReceivedPacket(uint16_t seq_num, bool is_keyframe);
+  int OnReceivedPacket(uint16_t seq_num, bool is_keyframe, bool is_recovered);
+
+  void ClearUpTo(uint16_t seq_num);
+  void UpdateRtt(int64_t rtt_ms);
+
+ private:
+  // Which fields to consider when deciding which packet to nack in
+  // GetNackBatch.
+  enum NackFilterOptions { kSeqNumOnly, kTimeOnly, kSeqNumAndTime };
+
+  // This class holds the sequence number of the packet that is in the nack list
+  // as well as the meta data about when it should be nacked and how many times
+  // we have tried to nack this packet.
+  struct NackInfo {
+    NackInfo();
+    NackInfo(uint16_t seq_num,
+             uint16_t send_at_seq_num,
+             Timestamp created_at_time);
+
+    uint16_t seq_num;
+    uint16_t send_at_seq_num;
+    Timestamp created_at_time;
+    Timestamp sent_at_time;
+    int retries;
+  };
+
+  void AddPacketsToNack(uint16_t seq_num_start, uint16_t seq_num_end)
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(worker_thread_);
+
+  // Removes packets from the nack list until the next keyframe. Returns true
+  // if packets were removed.
+  bool RemovePacketsUntilKeyFrame()
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(worker_thread_);
+  std::vector<uint16_t> GetNackBatch(NackFilterOptions options)
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(worker_thread_);
+
+  // Update the reordering distribution.
+  void UpdateReorderingStatistics(uint16_t seq_num)
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(worker_thread_);
+
+  // Returns how many packets we have to wait in order to receive the packet
+  // with probability `probabilty` or higher.
+  int WaitNumberOfPackets(float probability) const
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(worker_thread_);
+
+  TaskQueueBase* const worker_thread_;
+  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_
+      RTC_GUARDED_BY(worker_thread_);
+  std::set<uint16_t, DescendingSeqNumComp<uint16_t>> keyframe_list_
+      RTC_GUARDED_BY(worker_thread_);
+  std::set<uint16_t, DescendingSeqNumComp<uint16_t>> recovered_list_
+      RTC_GUARDED_BY(worker_thread_);
+  video_coding::Histogram reordering_histogram_ RTC_GUARDED_BY(worker_thread_);
+  bool initialized_ RTC_GUARDED_BY(worker_thread_);
+  TimeDelta rtt_ RTC_GUARDED_BY(worker_thread_);
+  uint16_t newest_seq_num_ RTC_GUARDED_BY(worker_thread_);
+
+  // Adds a delay before send nack on packet received.
+  const TimeDelta send_nack_delay_;
+
+  ScopedNackPeriodicProcessorRegistration processor_registration_;
+
+  // Used to signal destruction to potentially pending tasks.
+  ScopedTaskSafety task_safety_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_VIDEO_CODING_NACK_REQUESTER_H_