Pull out the PostFilter to its own NonlinearBeamformer API

webrtc/modules/audio_processing/beamformer/nonlinear_beamformer_test.cc

Index: webrtc/modules/audio_processing/beamformer/nonlinear_beamformer_test.cc
diff --git a/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer_test.cc b/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer_test.cc
index d1875526920cde162c5fe5492e545a577d073a5a..013d0b727deff187c9753765676a96a21cb5a845 100644
--- a/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer_test.cc
+++ b/webrtc/modules/audio_processing/beamformer/nonlinear_beamformer_test.cc
@@ -58,26 +58,25 @@ int main(int argc, char* argv[]) {
   printf("Output file: %s\nChannels: %" PRIuS ", Sample rate: %d Hz\n\n",
          FLAGS_o.c_str(), out_file.num_channels(), out_file.sample_rate());
 
-  ChannelBuffer<float> in_buf(
+  ChannelBuffer<float> buf(
       rtc::CheckedDivExact(in_file.sample_rate(), kChunksPerSecond),
       in_file.num_channels());
-  ChannelBuffer<float> out_buf(
-      rtc::CheckedDivExact(out_file.sample_rate(), kChunksPerSecond),
-      out_file.num_channels());
 
-  std::vector<float> interleaved(in_buf.size());
+  std::vector<float> interleaved(buf.size());
   while (in_file.ReadSamples(interleaved.size(),
                              &interleaved[0]) == interleaved.size()) {
+    buf.set_num_channels(in_file.num_channels());
     FloatS16ToFloat(&interleaved[0], interleaved.size(), &interleaved[0]);
-    Deinterleave(&interleaved[0], in_buf.num_frames(),
-                 in_buf.num_channels(), in_buf.channels());
+    Deinterleave(&interleaved[0], buf.num_frames(),
+                 buf.num_channels(), buf.channels());
 
-    bf.ProcessChunk(in_buf, &out_buf);
+    bf.ProcessChunk(&buf);
+    bf.PostFilter(&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());
+    Interleave(buf.channels(), buf.num_frames(),
+               buf.num_channels(), &interleaved[0]);
+    FloatToFloatS16(buf.channels()[0], buf.num_frames(), &interleaved[0]);
+    out_file.WriteSamples(&interleaved[0], buf.num_frames());
   }
 
   return 0;