[Device Discovery] Make DialRegistry a Singleton

chrome/browser/media/router/discovery/dial/dial_registry_factory.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_DIAL_DIAL_REGISTRY_FACTORY_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DIAL_REGISTRY_FACTORY_H_
+
+#include "base/macros.h"
+#include "base/memory/singleton.h"
+#include "components/keyed_service/content/refcounted_browser_context_keyed_service_factory.h"
+
+namespace content {
+class BrowserContext;
+}
+
+namespace media_router {
+
+class DialRegistry;
+
+// A factory that lazily returns a DialRegistry implementation for a given
+// BrowserContext.
+class DialRegistryFactory : public RefcountedBrowserContextKeyedServiceFactory {
+ public:
+  static scoped_refptr<DialRegistry> GetForBrowserContext(

[mark a. foltz, 2017/03/18 18:04:58]

If DialRegistry is not profile-keyed, this could just be DialRegistry::Get()
which manages a base::Singleton - no factory object required.

[zhaobin, 2017/03/22 02:48:45]

Done.

+      content::BrowserContext* context);
+
+  static DialRegistryFactory* GetInstance();
+
+ private:
+  friend struct base::DefaultSingletonTraits<DialRegistryFactory>;
+
+  DialRegistryFactory();
+  ~DialRegistryFactory() override;
+
+  // BrowserContextKeyedServiceFactory interface.
+  content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const override;
+
+  scoped_refptr<RefcountedKeyedService> BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+
+  DISALLOW_COPY_AND_ASSIGN(DialRegistryFactory);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_DISCOVERY_DIAL_DIAL_REGISTRY_FACTORY_H_