Remove unused method OutputMixer::PlayDtmfTone() and infrastructure.

webrtc/voice_engine/voice_engine.gyp

 # Copyright (c) 2011 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.
 
 {
   'includes': [
@@ skipping 34 matching lines @@
         'include/voe_network.h',
         'include/voe_rtp_rtcp.h',
         'include/voe_video_sync.h',
         'include/voe_volume_control.h',
         'channel.cc',
         'channel.h',
         'channel_manager.cc',
         'channel_manager.h',
         'channel_proxy.cc',
         'channel_proxy.h',
-        'dtmf_inband.cc',
-        'dtmf_inband.h',
         'level_indicator.cc',
         'level_indicator.h',
         'monitor_module.cc',
         'monitor_module.h',
         'network_predictor.cc',
         'network_predictor.h',
         'output_mixer.cc',
         'output_mixer.h',
         'shared_data.cc',
         'shared_data.h',
@@ skipping 218 matching lines @@
               'sources': [
                 'voe_auto_test.isolate',
               ],
             },
           ],
         }],
       ],  # conditions
     }], # include_tests==1
   ], # conditions
 }