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

chrome/browser/ui/media_utils.cc

Index: chrome/browser/ui/media_utils.cc
diff --git a/chrome/browser/ui/media_utils.cc b/chrome/browser/ui/media_utils.cc
index bae2e2e115274f532b04ae6b1d7959b847778e86..e5ffd493d8d6a9cdfd26c381bd7c0f4728986123 100644
--- a/chrome/browser/ui/media_utils.cc
+++ b/chrome/browser/ui/media_utils.cc
@@ -65,3 +65,11 @@ bool CheckMediaAccessPermission(content::WebContents* web_contents,
       ->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);
+}