Adding SmoothingFilter to audio network adaptor.

webrtc/modules/audio_coding/audio_network_adaptor/audio_network_adaptor.gypi

 # 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.
 
 {
   'targets': [
     { 'target_name': 'audio_network_adaptor',
       'type': 'static_library',
       'sources': [
         'audio_network_adaptor.cc',
         'audio_network_adaptor_impl.cc',
         'audio_network_adaptor_impl.h',
         'bitrate_controller.h',
         'bitrate_controller.cc',
         'channel_controller.cc',
         'channel_controller.h',
         'controller.h',
         'controller.cc',
         'controller_manager.cc',
         'controller_manager.h',
         'dtx_controller.h',
         'dtx_controller.cc',
-        'include/audio_network_adaptor.h'
+        'include/audio_network_adaptor.h',
+        'smoothing_filter.h',
+        'smoothing_filter.cc',
       ], # source
     },
   ], # targets
 }