[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_sinks_observer.h

Index: chrome/browser/media/router/media_sinks_observer.h
diff --git a/chrome/browser/media/router/media_sinks_observer.h b/chrome/browser/media/router/media_sinks_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..0516953694e0b4eb1e3aeba7bdb2a0c90b17462e
--- /dev/null
+++ b/chrome/browser/media/router/media_sinks_observer.h
@@ -0,0 +1,46 @@
+// Copyright 2015 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_SINKS_OBSERVER_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SINKS_OBSERVER_H_
+
+#include <map>

[Kevin M, 2015/03/26 20:50:14]

Not needed

[imcheng, 2015/03/26 23:33:13]

Done.

+#include <set>
+#include <vector>

[Kevin M, 2015/03/26 20:50:15]

Not needed

[imcheng, 2015/03/26 23:33:13]

Done.

+
+#include "chrome/browser/media/router/media_route.h"

[Kevin M, 2015/03/26 20:50:14]

Not needed

[imcheng, 2015/03/26 23:33:13]

Done.

+#include "chrome/browser/media/router/media_sink.h"
+#include "chrome/browser/media/router/media_source.h"
+
+namespace media_router {
+
+struct SinksQueryResult {
+  SinksQueryResult();

[Kevin M, 2015/03/26 20:50:14]

No ctor/dtor

[imcheng, 2015/03/26 23:33:13]

Needed by compiler.

+  ~SinksQueryResult();
+
+  std::vector<MediaSink> sinks;
+};
+
+// Interface for observing when the set of sinks compatible with a MediaSource

[Kevin M, 2015/03/26 20:50:15]

"set" => list || collection

[imcheng, 2015/03/26 23:33:13]

Changed to collection.

+// has been updated.

[Kevin M, 2015/03/26 20:50:14]

Can you add a comment about why this is just an interface? It's unclear from the
comments what is the purpose of having this be an abstract class. 

[imcheng, 2015/03/26 23:33:13]

Added more comments.

+class MediaSinksObserver {
+ public:
+  // Constructs an observer that will observe for sinks compatible
+  // with |source|.
+  explicit MediaSinksObserver(const MediaSource& source) : source_(source) {}
+  virtual ~MediaSinksObserver() {}
+
+  // This function is invoked when the list of sinks compatible
+  // with |source_| has been updated.
+  virtual void OnSinksReceived(const SinksQueryResult& result) = 0;
+
+  const MediaSource& source() const { return source_; }
+
+ private:
+  MediaSource source_;
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_SINKS_OBSERVER_H_