Make GetConfig() part of the AudioProcessing interface

webrtc/modules/audio_processing/include/audio_processing.cc

 /*
  *  Copyright (c) 2016 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 13 matching lines @@
 
 Beamforming::Beamforming(bool enabled,
                          const std::vector<Point>& array_geometry,
                          SphericalPointf target_direction)
     : enabled(enabled),
       array_geometry(array_geometry),
       target_direction(target_direction) {}
 
 Beamforming::~Beamforming() {}
 
+AudioProcessing::Config AudioProcessing::GetConfig() const {
+  return AudioProcessing::Config();
+}
 
 }  // namespace webrtc