Support 3 channels for audio input.

content/renderer/media/webrtc_audio_capturer.cc

Index: content/renderer/media/webrtc_audio_capturer.cc
diff --git a/content/renderer/media/webrtc_audio_capturer.cc b/content/renderer/media/webrtc_audio_capturer.cc
index 5ad35a2d2b7f581d8f3eb84f0a50a2d16cd14e02..c4de8e905c1a9e0446fc9210d4d6337f05b3033e 100644
--- a/content/renderer/media/webrtc_audio_capturer.cc
+++ b/content/renderer/media/webrtc_audio_capturer.cc
@@ -173,7 +173,8 @@ bool WebRtcAudioCapturer::Initialize() {
 
   // Verify that the reported input channel configuration is supported.
   if (channel_layout != media::CHANNEL_LAYOUT_MONO &&
-      channel_layout != media::CHANNEL_LAYOUT_STEREO) {
+      channel_layout != media::CHANNEL_LAYOUT_STEREO &&
+      channel_layout != media::CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC) {
     DLOG(ERROR) << channel_layout
                 << " is not a supported input channel configuration.";
     return false;