Reland of Make default media device ID salts random by default

chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_api.cc

 // Copyright 2013 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 "chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_api.h"
 
 #include <utility>
+#include <vector>
 
 #include "base/lazy_instance.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/task_runner_util.h"
 #include "chrome/browser/extensions/api/tabs/tabs_constants.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/media_device_id.h"
 #include "content/public/browser/web_contents.h"
@@ skipping 184 matching lines @@
 
   url::Origin security_origin(source_url().GetOrigin());
   return content::GetHMACForMediaDeviceID(device_id_salt(), security_origin,
                                           raw_id);
 }
 
 void WebrtcAudioPrivateFunction::InitDeviceIDSalt() {
   device_id_salt_ = GetProfile()->GetResourceContext()->GetMediaDeviceIDSalt();
 }
 
-const content::ResourceContext::SaltCallback&
-WebrtcAudioPrivateFunction::device_id_salt() const {
-  DCHECK(!device_id_salt_.is_null());
+std::string WebrtcAudioPrivateFunction::device_id_salt() const {
   return device_id_salt_;
 }
 
 bool WebrtcAudioPrivateGetSinksFunction::RunAsync() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   InitDeviceIDSalt();
   GetOutputDeviceNames();
 
   return true;
@@ skipping 273 matching lines @@
     results_.reset(wap::GetAssociatedSink::Results::Create("").release());
   } else {
     results_.reset(
         wap::GetAssociatedSink::Results::Create(associated_sink_id).release());
   }
 
   SendResponse(true);
 }
 
 }  // namespace extensions