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

content/public/browser/web_contents_delegate.h

 // 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <set>
@@ skipping 461 matching lines @@
       const MediaStreamRequest& request,
       const MediaResponseCallback& callback);
 
   // Checks if we have permission to access the microphone or camera. Note that
   // this does not query the user. |type| must be MEDIA_DEVICE_AUDIO_CAPTURE
   // or MEDIA_DEVICE_VIDEO_CAPTURE.
   virtual bool CheckMediaAccessPermission(WebContents* web_contents,
                                           const GURL& security_origin,
                                           MediaStreamType type);
 
+  // Returns the ID of the default device for the given media device |type|.
+  // If the returned value is an empty string, it means that there is no
+  // default device for the given |type|.
+  virtual std::string GetDefaultMediaDeviceId(WebContents* web_contents,
+                                              MediaStreamType type);
+
 #if defined(OS_ANDROID)
   // Asks permission to decode media stream. After permission is determined,
   // |callback| will be called with the result.
   virtual void RequestMediaDecodePermission(
       WebContents* web_contents,
       const base::Callback<void(bool)>& callback);
 
   // Creates a view embedding the video view.
   virtual base::android::ScopedJavaLocalRef<jobject>
       GetContentVideoViewEmbedder();
@@ skipping 75 matching lines @@
   // Called when |this| is no longer the WebContentsDelegate for |source|.
   void Detach(WebContents* source);
 
   // The WebContents that this is currently a delegate for.
   std::set<WebContents*> attached_contents_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_