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diff --git a/third_party/libwebrtc/video/call_stats2.h b/third_party/libwebrtc/video/call_stats2.h
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+++ b/third_party/libwebrtc/video/call_stats2.h
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+/*
+ *  Copyright (c) 2020 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 VIDEO_CALL_STATS2_H_
+#define VIDEO_CALL_STATS2_H_
+
+#include <list>
+#include <memory>
+
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/units/timestamp.h"
+#include "modules/include/module_common_types.h"
+#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
+#include "rtc_base/task_utils/repeating_task.h"
+#include "system_wrappers/include/clock.h"
+
+namespace webrtc {
+namespace internal {
+
+class CallStats {
+ public:
+  // Time interval for updating the observers.
+  static constexpr TimeDelta kUpdateInterval = TimeDelta::Millis(1000);
+
+  // Must be created and destroyed on the same task_queue.
+  CallStats(Clock* clock, TaskQueueBase* task_queue);
+  ~CallStats();
+
+  CallStats(const CallStats&) = delete;
+  CallStats& operator=(const CallStats&) = delete;
+
+  // Ensure that necessary repeating tasks are started.
+  void EnsureStarted();
+
+  // Expose an RtcpRttStats implementation without inheriting from RtcpRttStats.
+  // That allows us to separate the threading model of how RtcpRttStats is
+  // used (mostly on a process thread) and how CallStats is used (mostly on
+  // the TQ/worker thread). Since for both cases, there is a LastProcessedRtt()
+  // method, this separation allows us to not need a lock for either.
+  RtcpRttStats* AsRtcpRttStats() { return &rtcp_rtt_stats_impl_; }
+
+  // Registers/deregisters a new observer to receive statistics updates.
+  // Must be called from the construction thread.
+  void RegisterStatsObserver(CallStatsObserver* observer);
+  void DeregisterStatsObserver(CallStatsObserver* observer);
+
+  // Expose `LastProcessedRtt()` from RtcpRttStats to the public interface, as
+  // it is the part of the API that is needed by direct users of CallStats.
+  int64_t LastProcessedRtt() const;
+
+  // Exposed for tests to test histogram support.
+  void UpdateHistogramsForTest() { UpdateHistograms(); }
+
+  // Helper struct keeping track of the time a rtt value is reported.
+  struct RttTime {
+    RttTime(int64_t new_rtt, int64_t rtt_time) : rtt(new_rtt), time(rtt_time) {}
+    const int64_t rtt;
+    const int64_t time;
+  };
+
+ private:
+  // Part of the RtcpRttStats implementation. Called by RtcpRttStatsImpl.
+  void OnRttUpdate(int64_t rtt);
+
+  void UpdateAndReport();
+
+  // This method must only be called when the process thread is not
+  // running, and from the construction thread.
+  void UpdateHistograms();
+
+  class RtcpRttStatsImpl : public RtcpRttStats {
+   public:
+    explicit RtcpRttStatsImpl(CallStats* owner) : owner_(owner) {}
+    ~RtcpRttStatsImpl() override = default;
+
+   private:
+    void OnRttUpdate(int64_t rtt) override {
+      // For video send streams (video/video_send_stream.cc), the RtpRtcp module
+      // is currently created on a transport worker TaskQueue and not the worker
+      // thread - which is what happens in other cases. We should probably fix
+      // that so that the call consistently comes in on the right thread.
+      owner_->OnRttUpdate(rtt);
+    }
+
+    int64_t LastProcessedRtt() const override {
+      // This call path shouldn't be used anymore. This impl is only for
+      // propagating the rtt from the RtpRtcp module, which does not call
+      // LastProcessedRtt(). Down the line we should consider removing
+      // LastProcessedRtt() and use the interface for event notifications only.
+      RTC_DCHECK_NOTREACHED() << "Legacy call path";
+      return 0;
+    }
+
+    CallStats* const owner_;
+  } rtcp_rtt_stats_impl_{this};
+
+  Clock* const clock_;
+
+  // Used to regularly call UpdateAndReport().
+  RepeatingTaskHandle repeating_task_ RTC_GUARDED_BY(task_queue_);
+
+  // The last RTT in the statistics update (zero if there is no valid estimate).
+  int64_t max_rtt_ms_ RTC_GUARDED_BY(task_queue_);
+
+  // Last reported average RTT value.
+  int64_t avg_rtt_ms_ RTC_GUARDED_BY(task_queue_);
+
+  int64_t sum_avg_rtt_ms_ RTC_GUARDED_BY(task_queue_);
+  int64_t num_avg_rtt_ RTC_GUARDED_BY(task_queue_);
+  int64_t time_of_first_rtt_ms_ RTC_GUARDED_BY(task_queue_);
+
+  // All Rtt reports within valid time interval, oldest first.
+  std::list<RttTime> reports_ RTC_GUARDED_BY(task_queue_);
+
+  // Observers getting stats reports.
+  std::list<CallStatsObserver*> observers_ RTC_GUARDED_BY(task_queue_);
+
+  TaskQueueBase* const task_queue_;
+
+  // Used to signal destruction to potentially pending tasks.
+  ScopedTaskSafety task_safety_;
+};
+
+}  // namespace internal
+}  // namespace webrtc
+
+#endif  // VIDEO_CALL_STATS2_H_