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/aec3/reverb_frequency_response.h

@@ -0,0 +1,53 @@
+/*
+ *  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_AEC3_REVERB_FREQUENCY_RESPONSE_H_
+#define MODULES_AUDIO_PROCESSING_AEC3_REVERB_FREQUENCY_RESPONSE_H_
+
+#include <array>
+#include <vector>
+
+#include "absl/types/optional.h"
+#include "api/array_view.h"
+#include "modules/audio_processing/aec3/aec3_common.h"
+
+namespace webrtc {
+
+// Class for updating the frequency response for the reverb.
+class ReverbFrequencyResponse {
+ public:
+  ReverbFrequencyResponse();
+  ~ReverbFrequencyResponse();
+
+  // Updates the frequency response estimate of the reverb.
+  void Update(const std::vector<std::array<float, kFftLengthBy2Plus1>>&
+                  frequency_response,
+              int filter_delay_blocks,
+              const absl::optional<float>& linear_filter_quality,
+              bool stationary_block);
+
+  // Returns the estimated frequency response for the reverb.
+  rtc::ArrayView<const float> FrequencyResponse() const {
+    return tail_response_;
+  }
+
+ private:
+  void Update(const std::vector<std::array<float, kFftLengthBy2Plus1>>&
+                  frequency_response,
+              int filter_delay_blocks,
+              float linear_filter_quality);
+
+  float average_decay_ = 0.f;
+  std::array<float, kFftLengthBy2Plus1> tail_response_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_AUDIO_PROCESSING_AEC3_REVERB_FREQUENCY_RESPONSE_H_