[cast_channel] Make CastSocketService a global leaky singleton

chrome/browser/media/router/discovery/mdns/cast_media_sink_service.h

 // Copyright 2017 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 CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_MDNS_CAST_MEDIA_SINK_SERVICE_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_MDNS_CAST_MEDIA_SINK_SERVICE_H_
 
 #include <memory>
 #include <set>
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/threading/thread_checker.h"
 #include "chrome/browser/media/router/discovery/mdns/dns_sd_delegate.h"
 #include "chrome/browser/media/router/discovery/mdns/dns_sd_registry.h"
 #include "chrome/browser/media/router/discovery/media_sink_service_base.h"
 #include "components/cast_channel/cast_channel_enum.h"
 #include "components/cast_channel/cast_socket.h"
+#include "content/public/browser/browser_thread.h"
 #include "net/base/ip_endpoint.h"
 
 namespace cast_channel {
 class CastSocketService;
 }  // namespace cast_channel
 
 namespace content {
 class BrowserContext;
 }  // namespace content
 
@@ skipping 83 matching lines @@
                                  int channel_id,
                                  bool audio_only);
 
   // Raw pointer to DnsSdRegistry instance, which is a global leaky singleton
   // and lives as long as the browser process.
   DnsSdRegistry* dns_sd_registry_ = nullptr;
 
   // Service list from current round of discovery.
   DnsSdRegistry::DnsSdServiceList current_services_;
 
-  // Service managing creating and removing cast channels.
-  scoped_refptr<cast_channel::CastSocketService> cast_socket_service_;
+  // Raw pointer of leaky singleton CastSocketService, which manages creating
+  // and removing Cast sockets.
+  cast_channel::CastSocketService* const cast_socket_service_;
+
+  std::unique_ptr<cast_channel::CastSocket::Observer,
+                  content::BrowserThread::DeleteOnIOThread>
+      observer_;
 
   THREAD_CHECKER(thread_checker_);
 
   DISALLOW_COPY_AND_ASSIGN(CastMediaSinkService);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_MDNS_CAST_MEDIA_SINK_SERVICE_H_