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/signal_model.h

@@ -0,0 +1,34 @@
+/*
+ *  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_SIGNAL_MODEL_H_
+#define MODULES_AUDIO_PROCESSING_NS_SIGNAL_MODEL_H_
+
+#include <array>
+
+#include "modules/audio_processing/ns/ns_common.h"
+
+namespace webrtc {
+
+struct SignalModel {
+  SignalModel();
+  SignalModel(const SignalModel&) = delete;
+  SignalModel& operator=(const SignalModel&) = delete;
+
+  float lrt;
+  float spectral_diff;
+  float spectral_flatness;
+  // Log LRT factor with time-smoothing.
+  std::array<float, kFftSizeBy2Plus1> avg_log_lrt;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_AUDIO_PROCESSING_NS_SIGNAL_MODEL_H_