[Device Discovery] Make DialRegistry a Singleton

chrome/browser/media/router/discovery/dial/dial_registry.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 "chrome/browser/media/router/discovery/dial/dial_registry.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
@@ skipping 11 matching lines @@
 using base::Time;
 using base::TimeDelta;
 using content::BrowserThread;
 using net::NetworkChangeNotifier;
 
 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),
       refresh_interval_delta_(refresh_interval),
       expiration_delta_(expiration),
       max_devices_(max_devices) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DCHECK_GT(max_devices_, 0U);
   NetworkChangeNotifier::AddNetworkChangeObserver(this);
 }
@@ skipping 200 matching lines @@
 
   // Reset watermark.
   last_event_registry_generation_ = registry_generation_;
 }
 
 std::string DialRegistry::NextLabel() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   return base::IntToString(++label_count_);
 }
 
+void DialRegistry::ShutdownOnUIThread() {}
+
 void DialRegistry::OnDiscoveryRequest(DialService* service) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   MaybeSendEvent();
 }
 
 void DialRegistry::OnDeviceDiscovered(DialService* service,
                                       const DialDeviceData& device) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
   // Adds |device| to our list of devices or updates an existing device, unless
@@ skipping 99 matching lines @@
   for (auto& observer : observers_)
     observer.OnDialDeviceEvent(devices);
 }
 
 void DialRegistry::OnDialError(DialErrorCode type) {
   for (auto& observer : observers_)
     observer.OnDialError(type);
 }
 
 }  // namespace media_router