Add a .gyp option to use dummy audio file devices.

webrtc/build/common.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.
 
 # This file contains common settings for building WebRTC components.
 
@@ skipping 191 matching lines @@
       ['build_with_chromium==1', {
         # Build sources requiring GTK. NOTICE: This is not present in Chrome OS
         # build environments, even if available for Chromium builds.
         'use_gtk%': 0,
         # Exclude pulse audio on Chromium since its prerequisites don't require
         # pulse audio.
         'include_pulse_audio%': 0,
 
         # Exclude internal ADM since Chromium uses its own IO handling.
         'include_internal_audio_device%': 0,
+        'use_dummy_audio_file_devices%': 0,

[kjellander_webrtc, 2016/08/16 06:20:05]

If the default value is going to be the same for Chromium and non-Chromium
builds, please move the declaration of the variable to the section above this
instead (e.g. line 175).

[noahric, 2016/08/16 21:02:37]

Done. Also added an explanatory comment.

 
         # Remove tests for Chromium to avoid slowing down GYP generation.
         'include_tests%': 0,
         'restrict_webrtc_logging%': 1,
       }, {  # Settings for the standalone (not-in-Chromium) build.
         'use_gtk%': 1,
         # TODO(andrew): For now, disable the Chrome plugins, which causes a
         # flood of chromium-style warnings. Investigate enabling them:
         # http://code.google.com/p/webrtc/issues/detail?id=163
         'clang_use_chrome_plugins%': 0,
 
         'include_pulse_audio%': 1,
         'include_internal_audio_device%': 1,
+        'use_dummy_audio_file_devices%': 0,
         'include_tests%': 1,
         'restrict_webrtc_logging%': 0,
       }],
       ['target_arch=="arm" or target_arch=="arm64" or target_arch=="mipsel"', {
         'prefer_fixed_point%': 1,
       }],
       ['(target_arch=="arm" and arm_neon==1) or target_arch=="arm64"', {
         'build_with_neon%': 1,
       }],
       ['OS!="ios" and (target_arch!="arm" or arm_version>=7) and target_arch!="mips64el"', {
@@ skipping 363 matching lines @@
         }],
         ['OS=="freebsd"', {
           'defines': [
             'FREEBSD',
           ],
         }],
       ],
     },
   }, # target_defaults
 }