Add adaptive notch filter to remove narrowband echo components in AEC3

webrtc/modules/audio_processing/aec3/render_signal_analyzer.h

 /*
  *  Copyright (c) 2017 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.
  */
 
@@ skipping 25 matching lines @@
     RTC_DCHECK_LT(2, narrow_band_counters_.size());
     return std::any_of(narrow_band_counters_.begin(),
                        narrow_band_counters_.end(),
                        [](size_t a) { return a > 10; });
   }
 
   // Zeros the array around regions with narrow bands signal characteristics.
   void MaskRegionsAroundNarrowBands(
       std::array<float, kFftLengthBy2Plus1>* v) const;
 
+  rtc::Optional<int> NarrowPeakBand() const { return narrow_peak_band_; }
+
  private:
   std::array<size_t, kFftLengthBy2 - 1> narrow_band_counters_;
+  rtc::Optional<int> narrow_peak_band_;
+  size_t narrow_peak_counter_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(RenderSignalAnalyzer);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_RENDER_SIGNAL_ANALYZER_H_