Makes the WebRTC fake device capable of playing audio from a file.

media/base/media_switches.cc

Index: media/base/media_switches.cc
diff --git a/media/base/media_switches.cc b/media/base/media_switches.cc
index ad7a7eabac01244852ec5218397afbb0f014563c..fdee13666e00b9ceb6ca45b28d34efe17adc8dcf 100644
--- a/media/base/media_switches.cc
+++ b/media/base/media_switches.cc
@@ -91,9 +91,16 @@ const char kUseCras[] = "use-cras";
 // Use fake device for Media Stream to replace actual camera and microphone.
 const char kUseFakeDeviceForMediaStream[] = "use-fake-device-for-media-stream";
 
-// Use a raw video file as fake video capture device.
+// Use an .y4m file to play as the webcam. See the comments in
+// media/video/capture/file_video_capture_device.h for more details.
 const char kUseFileForFakeVideoCapture[] = "use-file-for-fake-video-capture";
 
+// Play a 44.1 kHz, 16-bit, little-endian .wav file as the microphone. Note that
+// for WebRTC calls we'll treat the bits as if they came from the microphone,
+// which means you should disable audio processing (lest your audio file will
+// play back distorted).
+const char kUseFileForFakeAudioCapture[] = "use-file-for-fake-audio-capture";
+
 // Enables support for inband text tracks in media content.
 const char kEnableInbandTextTracks[] = "enable-inband-text-tracks";