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

chrome/browser/ui/media_utils.cc

 // Copyright 2013 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/ui/media_utils.h"
 
 #include "chrome/browser/media/webrtc/media_capture_devices_dispatcher.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/web_contents.h"
 #include "extensions/features/features.h"
@@ skipping 47 matching lines @@
         ->CheckMediaAccessPermission(
             web_contents, security_origin, type, extension);
   }
   return MediaCaptureDevicesDispatcher::GetInstance()
       ->CheckMediaAccessPermission(web_contents, security_origin, type);
 #else
   return MediaCaptureDevicesDispatcher::GetInstance()
       ->CheckMediaAccessPermission(web_contents, security_origin, type);
 #endif
 }
+
+std::string GetDefaultMediaDeviceId(content::WebContents* web_contents,
+                                    content::MediaStreamType type) {
+  Profile* profile =
+      Profile::FromBrowserContext(web_contents->GetBrowserContext());
+  return MediaCaptureDevicesDispatcher::GetInstance()
+      ->GetDefaultDeviceIdForProfile(profile, type);
+}