Add adaptive notch filter to remove narrowband echo components in AEC3

webrtc/modules/audio_processing/aec3/render_signal_analyzer.h

Index: webrtc/modules/audio_processing/aec3/render_signal_analyzer.h
diff --git a/webrtc/modules/audio_processing/aec3/render_signal_analyzer.h b/webrtc/modules/audio_processing/aec3/render_signal_analyzer.h
index 9cabea2e6685045183223f5a0ab3ba406381d8f0..b0b56cde9e327222a4f2526bd781f957f1227752 100644
--- a/webrtc/modules/audio_processing/aec3/render_signal_analyzer.h
+++ b/webrtc/modules/audio_processing/aec3/render_signal_analyzer.h
@@ -43,8 +43,12 @@ class RenderSignalAnalyzer {
   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);
 };