Transparency improvements in the echo canceller 3

webrtc/modules/audio_processing/aec3/subtractor.h

Index: webrtc/modules/audio_processing/aec3/subtractor.h
diff --git a/webrtc/modules/audio_processing/aec3/subtractor.h b/webrtc/modules/audio_processing/aec3/subtractor.h
index c194b2ca1fd7459ab9ad36d79e87ab23341a4c56..777e4ff350e5809e5aa3a3d136946202c8f53458 100644
--- a/webrtc/modules/audio_processing/aec3/subtractor.h
+++ b/webrtc/modules/audio_processing/aec3/subtractor.h
@@ -45,12 +45,18 @@ class Subtractor {
 
   void HandleEchoPathChange(const EchoPathVariability& echo_path_variability);
 
-  // Returns the block-wise frequency response of the main adaptive filter.
+  // Returns the block-wise frequency response for the main adaptive filter.
   const std::vector<std::array<float, kFftLengthBy2Plus1>>&
   FilterFrequencyResponse() const {
     return main_filter_.FilterFrequencyResponse();
   }
 
+  // Returns the estimate of the impulse response for the main adaptive filter.
+  const std::array<float, kAdaptiveFilterTimeDomainLength>&
+  FilterImpulseResponse() const {
+    return main_filter_.FilterImpulseResponse();
+  }
+
  private:
   const Aec3Fft fft_;
   ApmDataDumper* data_dumper_;