Add functionality to get default media device IDs from user preferences.

chrome/browser/media/webrtc/media_capture_devices_dispatcher.cc

Index: chrome/browser/media/webrtc/media_capture_devices_dispatcher.cc
diff --git a/chrome/browser/media/webrtc/media_capture_devices_dispatcher.cc b/chrome/browser/media/webrtc/media_capture_devices_dispatcher.cc
index cf79263665dea1aae09a4f38e57a0804611c5675..57d8883cebf26403fe03ede934d365f5471a3cfe 100644
--- a/chrome/browser/media/webrtc/media_capture_devices_dispatcher.cc
+++ b/chrome/browser/media/webrtc/media_capture_devices_dispatcher.cc
@@ -234,6 +234,18 @@ void MediaCaptureDevicesDispatcher::GetDefaultDevicesForProfile(
   }
 }
 
+std::string MediaCaptureDevicesDispatcher::GetDefaultDeviceIdForProfile(
+    Profile* profile,
+    content::MediaStreamType type) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  PrefService* prefs = profile->GetPrefs();
+  if (type == content::MEDIA_DEVICE_AUDIO_CAPTURE)
+    return prefs->GetString(prefs::kDefaultAudioCaptureDevice);
+  else if (type == content::MEDIA_DEVICE_VIDEO_CAPTURE)

[Peter Kasting, 2017/01/17 21:02:46]

Drive-by nit: No else after return

[Guido Urdaneta, 2017/01/18 15:03:59]

Done.

+    return prefs->GetString(prefs::kDefaultVideoCaptureDevice);
+  return std::string();
+}
+
 const content::MediaStreamDevice*
 MediaCaptureDevicesDispatcher::GetRequestedAudioDevice(
     const std::string& requested_audio_device_id) {