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diff --git a/third_party/libwebrtc/audio/audio_level.h b/third_party/libwebrtc/audio/audio_level.h
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+++ b/third_party/libwebrtc/audio/audio_level.h
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+/*
+ *  Copyright (c) 2011 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 AUDIO_AUDIO_LEVEL_H_
+#define AUDIO_AUDIO_LEVEL_H_
+
+#include "rtc_base/synchronization/mutex.h"
+#include "rtc_base/thread_annotations.h"
+
+namespace webrtc {
+
+class AudioFrame;
+namespace voe {
+
+// This class is thread-safe. However, TotalEnergy() and TotalDuration() are
+// related, so if you call ComputeLevel() on a different thread than you read
+// these values, you still need to use lock to read them as a pair.
+class AudioLevel {
+ public:
+  AudioLevel();
+  ~AudioLevel();
+  void Reset();
+
+  // Returns the current audio level linearly [0,32767], which gets updated
+  // every "kUpdateFrequency+1" call to ComputeLevel() based on the maximum
+  // audio level of any audio frame, decaying by a factor of 1/4 each time
+  // LevelFullRange() gets updated.
+  // Called on "API thread(s)" from APIs like VoEBase::CreateChannel(),
+  // VoEBase::StopSend().
+  int16_t LevelFullRange() const;
+  void ResetLevelFullRange();
+  // See the description for "totalAudioEnergy" in the WebRTC stats spec
+  // (https://w3c.github.io/webrtc-stats/#dom-rtcaudiohandlerstats-totalaudioenergy)
+  // In our implementation, the total audio energy increases by the
+  // energy-equivalent of LevelFullRange() at the time of ComputeLevel(), rather
+  // than the energy of the samples in that specific audio frame. As a result,
+  // we may report a higher audio energy and audio level than the spec mandates.
+  // TODO(https://crbug.com/webrtc/10784): We should either do what the spec
+  // says or update the spec to match our implementation. If we want to have a
+  // decaying audio level we should probably update both the spec and the
+  // implementation to reduce the complexity of the definition. If we want to
+  // continue to have decaying audio we should have unittests covering the
+  // behavior of the decay.
+  double TotalEnergy() const;
+  double TotalDuration() const;
+
+  // Called on a native capture audio thread (platform dependent) from the
+  // AudioTransport::RecordedDataIsAvailable() callback.
+  // In Chrome, this method is called on the AudioInputDevice thread.
+  void ComputeLevel(const AudioFrame& audioFrame, double duration);
+
+ private:
+  enum { kUpdateFrequency = 10 };
+
+  mutable Mutex mutex_;
+
+  int16_t abs_max_ RTC_GUARDED_BY(mutex_);
+  int16_t count_ RTC_GUARDED_BY(mutex_);
+  int16_t current_level_full_range_ RTC_GUARDED_BY(mutex_);
+
+  double total_energy_ RTC_GUARDED_BY(mutex_) = 0.0;
+  double total_duration_ RTC_GUARDED_BY(mutex_) = 0.0;
+};
+
+}  // namespace voe
+}  // namespace webrtc
+
+#endif  // AUDIO_AUDIO_LEVEL_H_