Make GetConfig() part of the AudioProcessing interface

webrtc/modules/audio_processing/audio_processing_impl.h

Index: webrtc/modules/audio_processing/audio_processing_impl.h
diff --git a/webrtc/modules/audio_processing/audio_processing_impl.h b/webrtc/modules/audio_processing/audio_processing_impl.h
index 01b640fcfc0f36332790765fd530f267690cfc9a..79931499cdae78e05e2d233ae8b5447a5f38d666 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.h
+++ b/webrtc/modules/audio_processing/audio_processing_impl.h
@@ -134,9 +134,9 @@ class AudioProcessingImpl : public AudioProcessing {
   NoiseSuppression* noise_suppression() const override;
   VoiceDetection* voice_detection() const override;
 
-  // TODO(peah): Remove these two methods once the new API allows that.
+  // TODO(peah): Remove MutateConfig once the new API allows that.
   void MutateConfig(rtc::FunctionView<void(AudioProcessing::Config*)> mutator);
-  AudioProcessing::Config GetConfig() const;
+  AudioProcessing::Config GetConfig() const override;
 
  protected:
   // Overridden in a mock.