[cast_channel] Make CastSocket not inherit from ApiResource

extensions/browser/api/cast_channel/cast_channel_service_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 EXTENSIONS_BROWSER_API_CAST_CHANNEL_CAST_CHANNEL_SERVICE_FACTORY_H_
+#define EXTENSIONS_BROWSER_API_CAST_CHANNEL_CAST_CHANNEL_SERVICE_FACTORY_H_
+
+#include "base/lazy_instance.h"
+#include "base/macros.h"
+#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
+
+namespace extensions {
+namespace api {
+namespace cast_channel {
+
+class CastChannelService;
+
+class CastChannelServiceFactory : public BrowserContextKeyedServiceFactory {

[mark a. foltz, 2017/05/18 18:02:27]

I think a CastSocket created by one profile (browser context) could be shared
with other profiles.  Ultimately the set of cast sockets will be determined by
the set of Cast devices available on the user's LAN, which is not a function of
the browser profile.  The Cast MRP should be responsible for not exposing any
information across profiles inappropriately (I don't think it cares whether the
socket is per-profile or shared).

I think this is fine to land as it matches existing behavior; but does
examination of the Cast MRP code reveal any issues with sharing sockets?

If not, then the CastChannelService could be refactored as a LazySingleton
without the need for a factory :)

[zhaobin, 2017/05/24 01:51:40]

Created crbug.com/725717

+ public:
+  static CastChannelService* GetForBrowserContext(
+      content::BrowserContext* context);
+
+  static CastChannelServiceFactory* GetInstance();
+
+ private:
+  friend struct base::LazyInstanceTraitsBase<CastChannelServiceFactory>;
+
+  CastChannelServiceFactory();
+  ~CastChannelServiceFactory() override;
+
+  // BrowserContextKeyedServiceFactory interface.
+  content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const override;
+
+  KeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+
+  DISALLOW_COPY_AND_ASSIGN(CastChannelServiceFactory);
+};
+
+}  // namespace cast_channel
+}  // namespace api
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_API_CAST_CHANNEL_CAST_CHANNEL_SERVICE_FACTORY_H_