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/ns/histograms.h

@@ -0,0 +1,55 @@
+/*
+ *  Copyright (c) 2019 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_NS_HISTOGRAMS_H_
+#define MODULES_AUDIO_PROCESSING_NS_HISTOGRAMS_H_
+
+#include <array>
+
+#include "api/array_view.h"
+#include "modules/audio_processing/ns/ns_common.h"
+#include "modules/audio_processing/ns/signal_model.h"
+
+namespace webrtc {
+
+constexpr int kHistogramSize = 1000;
+
+// Class for handling the updating of histograms.
+class Histograms {
+ public:
+  Histograms();
+  Histograms(const Histograms&) = delete;
+  Histograms& operator=(const Histograms&) = delete;
+
+  // Clears the histograms.
+  void Clear();
+
+  // Extracts thresholds for feature parameters and updates the corresponding
+  // histogram.
+  void Update(const SignalModel& features_);
+
+  // Methods for accessing the histograms.
+  rtc::ArrayView<const int, kHistogramSize> get_lrt() const { return lrt_; }
+  rtc::ArrayView<const int, kHistogramSize> get_spectral_flatness() const {
+    return spectral_flatness_;
+  }
+  rtc::ArrayView<const int, kHistogramSize> get_spectral_diff() const {
+    return spectral_diff_;
+  }
+
+ private:
+  std::array<int, kHistogramSize> lrt_;
+  std::array<int, kHistogramSize> spectral_flatness_;
+  std::array<int, kHistogramSize> spectral_diff_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_AUDIO_PROCESSING_NS_HISTOGRAMS_H_