[Media Router] (device discovery) Create MediaSinkService interface

chrome/browser/media/router/media_sink_service.h

Index: chrome/browser/media/router/media_sink_service.h
diff --git a/chrome/browser/media/router/media_sink_service.h b/chrome/browser/media/router/media_sink_service.h
new file mode 100644
index 0000000000000000000000000000000000000000..1145a4315e9eea76e81e7c5a863eccd0ca476cc1
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+++ b/chrome/browser/media/router/media_sink_service.h
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+// 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/browser/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>&)>;

[zhaobin, 2017/02/14 00:42:17]

Will change MediaSink to TypedMediaSink (or sth else) when we finalize design in
https://codereview.chromium.org/2675033002/.

+
+  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.
+  // 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 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_