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

webrtc/build/common.gypi

Index: webrtc/build/common.gypi
diff --git a/webrtc/build/common.gypi b/webrtc/build/common.gypi
index 265c3d78037bcdfd1c3ab3856d9c63a9e9802d04..4c7e96b20395be02a97c7b9325d87f1f19bc543e 100644
--- a/webrtc/build/common.gypi
+++ b/webrtc/build/common.gypi
@@ -209,6 +209,7 @@
 
         # 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,
@@ -222,6 +223,7 @@
 
         'include_pulse_audio%': 1,
         'include_internal_audio_device%': 1,
+        'use_dummy_audio_file_devices%': 0,
         'include_tests%': 1,
         'restrict_webrtc_logging%': 0,
       }],