Pull out the PostFilter to its own NonlinearBeamformer API

webrtc/modules/audio_processing/audio_processing.gypi

 # Copyright (c) 2012 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.
 
 {
   'variables': {
@@ skipping 48 matching lines @@
         'agc/legacy/digital_agc.h',
         'agc/legacy/gain_control.h',
         'agc/utility.cc',
         'agc/utility.h',
         'audio_buffer.cc',
         'audio_buffer.h',
         'audio_processing_impl.cc',
         'audio_processing_impl.h',
         'beamformer/array_util.cc',
         'beamformer/array_util.h',
-        'beamformer/beamformer.h',
         'beamformer/complex_matrix.h',
         'beamformer/covariance_matrix_generator.cc',
         'beamformer/covariance_matrix_generator.h',
         'beamformer/matrix.h',
         'beamformer/nonlinear_beamformer.cc',
         'beamformer/nonlinear_beamformer.h',
         'common.h',
         'echo_cancellation_impl.cc',
         'echo_cancellation_impl.h',
         'echo_control_mobile_impl.cc',
@@ skipping 225 matching lines @@
             'defines': ['WEBRTC_AEC_DEBUG_DUMP=1',],
           }],
           ['aec_debug_dump==0', {
             'defines': ['WEBRTC_AEC_DEBUG_DUMP=0',],
           }],
         ],
       }],
     }],
   ],
 }