Make default media device ID salts random by default

content/public/browser/resource_context.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_RESOURCE_CONTEXT_H_
 #define CONTENT_PUBLIC_BROWSER_RESOURCE_CONTEXT_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 59 matching lines @@
   // being torn down (on the IO thread). The current interface that
   // allows using the salt object after ResourceContext has gone away
   // was put in place to fix http://crbug.com/341211 but I intend to
   // try to figure out how the lifetime should be fixed properly. The
   // original interface was just a method that returns a string.
   //
   // TODO(perkj): Make this method pure virtual when crbug/315022 is
   // fixed.
   typedef base::Callback<std::string()> SaltCallback;
   virtual SaltCallback GetMediaDeviceIDSalt();
+
+  // Utility functions useful for implementations
+  static std::string CreateRandomMediaDeviceIDSalt();
+  static SaltCallback CreateSaltCallback(const std::string& salt);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_RESOURCE_CONTEXT_H_