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

chrome/browser/media/webrtc/media_capture_devices_dispatcher.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/media/webrtc/media_capture_devices_dispatcher.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 216 matching lines @@
     default_device = prefs->GetString(prefs::kDefaultVideoCaptureDevice);
     const content::MediaStreamDevice* device =
         GetRequestedVideoDevice(default_device);
     if (!device)
       device = GetFirstAvailableVideoDevice();
     if (device)
       devices->push_back(*device);
   }
 }
 
+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) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   const content::MediaStreamDevices& audio_devices = GetAudioCaptureDevices();
   const content::MediaStreamDevice* const device =
       FindDeviceWithId(audio_devices, requested_audio_device_id);
   return device;
 }
 
@@ skipping 199 matching lines @@
 #if BUILDFLAG(ENABLE_EXTENSIONS)
   for (MediaAccessHandler* handler : media_access_handlers_) {
     if (handler->SupportsStreamType(stream_type, nullptr)) {
       ToCaptureAccessHandlerBase(handler)->UpdateCapturingLinkSecured(
           render_process_id, render_frame_id, page_request_id, is_secure);
       break;
     }
   }
 #endif
 }