[Media Router] Add DialMediaSinkService and DeviceDescriptionService

chrome/browser/media/router/media_sink_service.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_MEDIA_SINK_SERVICE_H_
-#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SINK_SERVICE_H_
-
-#include <memory>
-#include <vector>
-
-#include "base/callback.h"
-#include "chrome/common/media_router/media_sink.h"
-
-namespace media_router {
-
-class MediaSinksObserver;
-
-// A service which can be used to start background discovery and resolution of
-// MediaSinks. Often these are remote devices, like Chromecast. In addition, the
-// service is capable of answering MediaSink queries using the sinks that it
-// generated.
-// This class is not thread safe. All methods must be called from the IO thread.
-class MediaSinkService {
- public:
-  // Callback to be invoked when this class finishes sink discovering.
-  // Arg 0: Sinks discovered and resolved by the service.
-  using OnSinksDiscoveredCallback =
-      base::Callback<void(const std::vector<MediaSink>&)>;
-
-  explicit MediaSinkService(
-      const OnSinksDiscoveredCallback& sinks_discovered_callback);
-
-  virtual ~MediaSinkService();
-
-  // Starts sink discovery. No-ops if already started.
-  // Sinks discovered and resolved are continuously passed to
-  // |callback|.
-  virtual void Start() = 0;
-
-  // Adds a sink query to observe for MediaSink updates.
-  // Multiple observers can be added for a given MediaSource.
-  // Start() must be called first. This class does not take
-  // ownership of |observer|.
-  virtual void AddSinkQuery(MediaSinksObserver* observer) = 0;
-
-  // Removes a sink query and stops observing MediaSink updates. No-op if
-  // |observer| is not registered with this class.
-  virtual void RemoveSinkQuery(MediaSinksObserver* observer) = 0;
-
- protected:
-  OnSinksDiscoveredCallback sinks_discovered_callback_;
-
-  DISALLOW_COPY_AND_ASSIGN(MediaSinkService);
-};
-
-}  // namespace media_router
-
-#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SINK_SERVICE_H_