Update to current webrtc library

This is from the upstream library commit id
3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium
88.0.4290.1.

webrtc/modules/audio_processing/agc2/saturation_protector.h

@@ -0,0 +1,82 @@
+/*
+ *  Copyright (c) 2018 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_AUDIO_PROCESSING_AGC2_SATURATION_PROTECTOR_H_
+#define MODULES_AUDIO_PROCESSING_AGC2_SATURATION_PROTECTOR_H_
+
+#include <array>
+
+#include "absl/types/optional.h"
+#include "modules/audio_processing/agc2/agc2_common.h"
+#include "rtc_base/numerics/safe_compare.h"
+
+namespace webrtc {
+namespace saturation_protector_impl {
+
+// Ring buffer which only supports (i) push back and (ii) read oldest item.
+class RingBuffer {
+ public:
+  bool operator==(const RingBuffer& b) const;
+  inline bool operator!=(const RingBuffer& b) const { return !(*this == b); }
+
+  // Maximum number of values that the buffer can contain.
+  int Capacity() const { return buffer_.size(); }
+  // Number of values in the buffer.
+  int Size() const { return size_; }
+
+  void Reset();
+  // Pushes back `v`. If the buffer is full, the oldest value is replaced.
+  void PushBack(float v);
+  // Returns the oldest item in the buffer. Returns an empty value if the
+  // buffer is empty.
+  absl::optional<float> Front() const;
+
+ private:
+  inline int FrontIndex() const {
+    return rtc::SafeEq(size_, buffer_.size()) ? next_ : 0;
+  }
+  // `buffer_` has `size_` elements (up to the size of `buffer_`) and `next_` is
+  // the position where the next new value is written in `buffer_`.
+  std::array<float, kPeakEnveloperBufferSize> buffer_;
+  int next_ = 0;
+  int size_ = 0;
+};
+
+}  // namespace saturation_protector_impl
+
+// Saturation protector state. Exposed publicly for check-pointing and restore
+// ops.
+struct SaturationProtectorState {
+  bool operator==(const SaturationProtectorState& s) const;
+  inline bool operator!=(const SaturationProtectorState& s) const {
+    return !(*this == s);
+  }
+
+  float margin_db;  // Recommended margin.
+  saturation_protector_impl::RingBuffer peak_delay_buffer;
+  float max_peaks_dbfs;
+  int time_since_push_ms;  // Time since the last ring buffer push operation.
+};
+
+// Resets the saturation protector state.
+void ResetSaturationProtectorState(float initial_margin_db,
+                                   SaturationProtectorState& state);
+
+// Updates `state` by analyzing the estimated speech level `speech_level_dbfs`
+// and the peak power `speech_peak_dbfs` for an observed frame which is
+// reliably classified as "speech". `state` must not be modified without calling
+// this function.
+void UpdateSaturationProtectorState(float speech_peak_dbfs,
+                                    float speech_level_dbfs,
+                                    SaturationProtectorState& state);
+
+}  // namespace webrtc
+
+#endif  // MODULES_AUDIO_PROCESSING_AGC2_SATURATION_PROTECTOR_H_