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diff --git a/third_party/libwebrtc/video/quality_threshold.h b/third_party/libwebrtc/video/quality_threshold.h
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+++ b/third_party/libwebrtc/video/quality_threshold.h
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+/*
+ *  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 VIDEO_QUALITY_THRESHOLD_H_
+#define VIDEO_QUALITY_THRESHOLD_H_
+
+#include <memory>
+
+#include "absl/types/optional.h"
+
+namespace webrtc {
+
+class QualityThreshold {
+ public:
+  // Both thresholds are inclusive, i.e. measurement >= high signifies a high
+  // state, while measurement <= low signifies a low state.
+  QualityThreshold(int low_threshold,
+                   int high_threshold,
+                   float fraction,
+                   int max_measurements);
+  ~QualityThreshold();
+
+  void AddMeasurement(int measurement);
+  absl::optional<bool> IsHigh() const;
+  absl::optional<double> CalculateVariance() const;
+  absl::optional<double> FractionHigh(int min_required_samples) const;
+
+ private:
+  const std::unique_ptr<int[]> buffer_;
+  const int max_measurements_;
+  const float fraction_;
+  const int low_threshold_;
+  const int high_threshold_;
+  int until_full_;
+  int next_index_;
+  absl::optional<bool> is_high_;
+  int sum_;
+  int count_low_;
+  int count_high_;
+  int num_high_states_;
+  int num_certain_states_;
+};
+
+}  // namespace webrtc
+
+#endif  // VIDEO_QUALITY_THRESHOLD_H_