Enable keyboard mic for WebRTC if supported on the device.

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 e47beeada9599414a4b77d88ab07eb3457584baf..3568f1a43996d51a131c02ad516d543d56c8839f 100644
--- a/content/renderer/media/webrtc_audio_capturer.cc
+++ b/content/renderer/media/webrtc_audio_capturer.cc
@@ -172,6 +172,21 @@ bool WebRtcAudioCapturer::Initialize() {
 
   media::ChannelLayout channel_layout = static_cast<media::ChannelLayout>(
       device_info_.device.input.channel_layout);
+
+  // If the KEYBOARD_MIC effect is set, change the layout to the corresponding
+  // layout that includes the keyboard mic.
+  if (device_info_.device.input.effects &
+      media::AudioParameters::KEYBOARD_MIC) {
+    if (channel_layout == media::CHANNEL_LAYOUT_STEREO) {
+      channel_layout = media::CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC;
+      DVLOG(1) << "Changed stereo layout to stereo + keyboard mic layout due "
+               << "to KEYBOARD_MIC effect.";
+    } else {
+      DVLOG(1) << "KEYBOARD_MIC effect ignored, not compatible with layout "
+               << channel_layout;
+    }
+  }
+
   DVLOG(1) << "Audio input hardware channel layout: " << channel_layout;
   UMA_HISTOGRAM_ENUMERATION("WebRTC.AudioInputChannelLayout",
                             channel_layout, media::CHANNEL_LAYOUT_MAX + 1);