Implement a salt for MediaSource IDs that can be cleared by a user.

content/public/test/mock_resource_context.cc

 // 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.
 
 #include "content/public/test/mock_resource_context.h"
 
 #include "net/url_request/url_request_context.h"
 
 namespace content {
 
@@ skipping 20 matching lines @@
 }
 
 bool MockResourceContext::AllowMicAccess(const GURL& origin)  {
   return mic_allowed_;
 }
 
 bool MockResourceContext::AllowCameraAccess(const GURL& origin)  {
   return camera_allowed_;
 }
 
+std::string MockResourceContext::GetMediaDeviceIDSalt() {
+  return "mock_salt";
+}
+
 }  // namespace content