Pull out the PostFilter to its own NonlinearBeamformer API

webrtc/modules/audio_processing/beamformer/nonlinear_beamformer_test.cc

 /*
  *  Copyright (c) 2014 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 55 matching lines @@
       out_file.num_channels());
 
   std::vector<float> interleaved(in_buf.size());
   while (in_file.ReadSamples(interleaved.size(),
                              &interleaved[0]) == interleaved.size()) {
     FloatS16ToFloat(&interleaved[0], interleaved.size(), &interleaved[0]);
     Deinterleave(&interleaved[0], in_buf.num_frames(),
                  in_buf.num_channels(), in_buf.channels());
 
     bf.ProcessChunk(in_buf, &out_buf);
+    bf.PostFilter(out_buf, &out_buf);
 
     Interleave(out_buf.channels(), out_buf.num_frames(),
                out_buf.num_channels(), &interleaved[0]);
     FloatToFloatS16(&interleaved[0], interleaved.size(), &interleaved[0]);
     out_file.WriteSamples(&interleaved[0], interleaved.size());
   }
 
   return 0;
 }
 
 }  // namespace webrtc
 
 int main(int argc, char* argv[]) {
   return webrtc::main(argc, argv);
 }