[Media Router] (device discovery) Create MediaSinkService interface

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 "base/callback_list.h"

[imcheng, 2017/02/07 00:48:14]

Did you mean to include base/callback.h ?

[zhaobin, 2017/02/07 02:38:50]

Done.

+#include "chrome/browser/media/router/media_sink.h"
+
+namespace media_router {
+
+class MediaSinksObserver;
+
+// MediaSinkService defines an interface which can be implemented by DIAL, Cast

[imcheng, 2017/02/07 00:48:13]

Comment suggestion:

A service which can be used to start device discovery and resolution in the
background to generate MediaSinks. In addition, the service is capable of
answering MediaSink queries using the sinks that it generated.

[zhaobin, 2017/02/07 02:38:50]

Done.

+// or future protocols to produce MediaSinks from device discovery/resolution.
+// The service is also responsible for answering MediaSink queries.

[imcheng, 2017/02/07 00:48:13]

Can you also document threading assumptions? e.g.,

This class is not thread safe. All methods must be called from the UI thread.

[zhaobin, 2017/02/07 02:38:50]

Done.

+class MediaSinkService {

[imcheng, 2017/02/07 00:48:14]

Please also define a virtual destructor.

[zhaobin, 2017/02/07 02:38:50]

Done.

+ public:
+  // Callback used for |Start()|.
+  // Arg 0: |this|
+  // Arg 1: Sinks discovered and resolved by the service.
+  using OnSinksDiscoveredCallback =
+      base::Callback<void(const const MediaSinkService*,

[imcheng, 2017/02/07 00:48:13]

Hmm, not quite sure if we still need to pass |this| anymore. Its original
purpose was to have MR get the name of the service to pass to MR extension, but
as discussed we don't need to do that.

[zhaobin, 2017/02/07 02:38:50]

Done.

+                          const std::vector<MediaSink>&)>;
+
+  // Starts sink discovery. No-ops if already started.
+  // Sinks discovered and resolved are continuously passed to
+  // |callback|.
+  virtual void Start(const OnSinksDiscoveredCallback& callback) = 0;
+
+  // Adds a sink query to observe for MediaSink updates.
+  // Only one observer 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 stop observing for MediaSink updates.
+  virtual void RemoveSinkQuery(MediaSinksObserver* observer) = 0;
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SINK_SERVICE_H_