[Device Discovery] Make DialRegistry a Singleton

chrome/browser/media/router/discovery/dial/dial_registry.cc

Index: chrome/browser/media/router/discovery/dial/dial_registry.cc
diff --git a/chrome/browser/media/router/discovery/dial/dial_registry.cc b/chrome/browser/media/router/discovery/dial/dial_registry.cc
index 11def8ff1deac094bedd6abe13b14adcac4f6c08..954a6260370f02415ade4790f14135aa02d1be80 100644
--- a/chrome/browser/media/router/discovery/dial/dial_registry.cc
+++ b/chrome/browser/media/router/discovery/dial/dial_registry.cc
@@ -29,7 +29,9 @@ namespace media_router {
 DialRegistry::DialRegistry(base::TimeDelta refresh_interval,
                            base::TimeDelta expiration,
                            const size_t max_devices)
-    : num_listeners_(0),
+    : RefcountedKeyedService(
+          BrowserThread::GetTaskRunnerForThread(BrowserThread::IO)),
+      num_listeners_(0),
       registry_generation_(0),
       last_event_registry_generation_(0),
       label_count_(0),
@@ -250,6 +252,8 @@ std::string DialRegistry::NextLabel() {
   return base::IntToString(++label_count_);
 }
 
+void DialRegistry::ShutdownOnUIThread() {}
+
 void DialRegistry::OnDiscoveryRequest(DialService* service) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   MaybeSendEvent();