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diff --git a/third_party/libwebrtc/rtc_base/rate_tracker.h b/third_party/libwebrtc/rtc_base/rate_tracker.h
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+/*
+ *  Copyright 2015 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 RTC_BASE_RATE_TRACKER_H_
+#define RTC_BASE_RATE_TRACKER_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+namespace rtc {
+
+// Computes units per second over a given interval by tracking the units over
+// each bucket of a given size and calculating the instantaneous rate assuming
+// that over each bucket the rate was constant.
+class RateTracker {
+ public:
+  RateTracker(int64_t bucket_milliseconds, size_t bucket_count);
+  virtual ~RateTracker();
+
+  // Computes the average rate over the most recent interval_milliseconds,
+  // or if the first sample was added within this period, computes the rate
+  // since the first sample was added.
+  double ComputeRateForInterval(int64_t interval_milliseconds) const;
+
+  // Computes the average rate over the rate tracker's recording interval
+  // of bucket_milliseconds * bucket_count.
+  double ComputeRate() const {
+    return ComputeRateForInterval(bucket_milliseconds_ *
+                                  static_cast<int64_t>(bucket_count_));
+  }
+
+  // Computes the average rate since the first sample was added to the
+  // rate tracker.
+  double ComputeTotalRate() const;
+
+  // The total number of samples added.
+  int64_t TotalSampleCount() const;
+
+  // Reads the current time in order to determine the appropriate bucket for
+  // these samples, and increments the count for that bucket by sample_count.
+  void AddSamples(int64_t sample_count);
+
+  // Increment count for bucket at `current_time_ms`.
+  void AddSamplesAtTime(int64_t current_time_ms, int64_t sample_count);
+
+ protected:
+  // overrideable for tests
+  virtual int64_t Time() const;
+
+ private:
+  void EnsureInitialized();
+  size_t NextBucketIndex(size_t bucket_index) const;
+
+  const int64_t bucket_milliseconds_;
+  const size_t bucket_count_;
+  int64_t* sample_buckets_;
+  size_t total_sample_count_;
+  size_t current_bucket_;
+  int64_t bucket_start_time_milliseconds_;
+  int64_t initialization_time_milliseconds_;
+};
+
+}  // namespace rtc
+
+#endif  // RTC_BASE_RATE_TRACKER_H_