[cast_channel] Make CastSocketService a global leaky singleton

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

Index: chrome/browser/media/router/discovery/mdns/cast_media_sink_service.cc
diff --git a/chrome/browser/media/router/discovery/mdns/cast_media_sink_service.cc b/chrome/browser/media/router/discovery/mdns/cast_media_sink_service.cc
index 1ad648bc2b645d98e5b9983a68b5b54c95ebff3f..022649b755f90a3e89e83184fc8367257c9af1b5 100644
--- a/chrome/browser/media/router/discovery/mdns/cast_media_sink_service.cc
+++ b/chrome/browser/media/router/discovery/mdns/cast_media_sink_service.cc
@@ -8,7 +8,6 @@
 #include "chrome/browser/browser_process.h"
 #include "chrome/common/media_router/discovery/media_sink_internal.h"
 #include "components/cast_channel/cast_socket_service.h"
-#include "components/cast_channel/cast_socket_service_factory.h"
 #include "components/net_log/chrome_net_log.h"
 #include "content/public/common/content_client.h"
 #include "net/base/host_port_pair.h"
@@ -16,8 +15,6 @@
 
 namespace {
 
-constexpr char kObserverId[] = "browser_observer_id";
-
 enum ErrorType {
   NONE,
   NOT_CAST_DEVICE,
@@ -90,10 +87,9 @@ const char CastMediaSinkService::kCastServiceType[] = "_googlecast._tcp.local";
 CastMediaSinkService::CastMediaSinkService(
     const OnSinksDiscoveredCallback& callback,
     content::BrowserContext* browser_context)
-    : MediaSinkServiceBase(callback) {
+    : MediaSinkServiceBase(callback),
+      cast_socket_service_(cast_channel::CastSocketService::GetInstance()) {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
-  cast_socket_service_ = cast_channel::CastSocketServiceFactory::GetInstance()
-                             ->GetForBrowserContext(browser_context);
   DCHECK(cast_socket_service_);
 }
 
@@ -169,17 +165,14 @@ void CastMediaSinkService::OnDnsSdEvent(
 void CastMediaSinkService::OpenChannelOnIOThread(
     const DnsSdService& service,
     const net::IPEndPoint& ip_endpoint) {
-  auto* observer = cast_socket_service_->GetObserver(kObserverId);
-  if (!observer) {
-    observer = new CastSocketObserver();
-    cast_socket_service_->AddObserver(kObserverId, base::WrapUnique(observer));
-  }
+  if (!observer_)
+    observer_.reset(new CastSocketObserver());
 
   cast_socket_service_->OpenSocket(
       ip_endpoint, g_browser_process->net_log(),
       base::Bind(&CastMediaSinkService::OnChannelOpenedOnIOThread, this,
                  service),
-      observer);
+      observer_.get());
 }
 
 void CastMediaSinkService::OnChannelOpenedOnIOThread(
@@ -228,7 +221,9 @@ void CastMediaSinkService::OnChannelOpenedOnUIThread(
 }
 
 CastMediaSinkService::CastSocketObserver::CastSocketObserver() {}
-CastMediaSinkService::CastSocketObserver::~CastSocketObserver() {}
+CastMediaSinkService::CastSocketObserver::~CastSocketObserver() {
+  cast_channel::CastSocketService::GetInstance()->RemoveObserver(this);
+}
 
 void CastMediaSinkService::CastSocketObserver::OnError(
     const cast_channel::CastSocket& socket,