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

content/browser/web_contents/web_contents_impl.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_BROWSER_WEB_CONTENTS_WEB_CONTENTS_IMPL_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_IMPL_H_
 
 #include <stdint.h>
 
 #include <functional>
@@ skipping 529 matching lines @@
                                  int32_t route_id) override;
   void ShowCreatedWidget(int process_id,
                          int route_id,
                          const gfx::Rect& initial_rect) override;
   void ShowCreatedFullscreenWidget(int process_id, int route_id) override;
   void RequestMediaAccessPermission(
       const MediaStreamRequest& request,
       const MediaResponseCallback& callback) override;
   bool CheckMediaAccessPermission(const GURL& security_origin,
                                   MediaStreamType type) override;
+  std::string GetDefaultMediaDeviceId(MediaStreamType type) override;
   SessionStorageNamespace* GetSessionStorageNamespace(
       SiteInstance* instance) override;
   SessionStorageNamespaceMap GetSessionStorageNamespaceMap() override;
   double GetPendingPageZoomLevel() override;
   FrameTree* GetFrameTree() override;
   void SetIsVirtualKeyboardRequested(bool requested) override;
   bool IsVirtualKeyboardRequested() override;
   bool IsOverridingUserAgent() override;
   bool IsJavaScriptDialogShowing() const override;
   bool HideDownloadUI() const override;
@@ skipping 956 matching lines @@
   // Adds/removes a callback called on creation of each new WebContents.
   static void AddCreatedCallbackForTesting(const CreatedCallback& callback);
   static void RemoveCreatedCallbackForTesting(const CreatedCallback& callback);
 
   DISALLOW_COPY_AND_ASSIGN(FriendZone);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_IMPL_H_