[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_sink.h

Index: chrome/browser/media/router/media_sink.h
diff --git a/chrome/browser/media/router/media_sink.h b/chrome/browser/media/router/media_sink.h
index af4e9a8d29501ff3913687a93725674ac63bf512..1110c75dd7b926562bca82ba6c8e0a22644cd1bf 100644
--- a/chrome/browser/media/router/media_sink.h
+++ b/chrome/browser/media/router/media_sink.h
@@ -18,18 +18,24 @@ class MediaSink {
  public:
   // |sink_id|: Unique identifier for the MediaSink.
   // |name|: Descriptive name of the MediaSink.
+  //         Optional, can use an empty string if no sink name is available.
   MediaSink(const MediaSinkId& sink_id,
             const std::string& name);
+
+  // Constructs an empty MediaSink.
+  MediaSink();
+
   ~MediaSink();
 
-  const MediaSinkId& sink_id() const { return sink_id_; }
+  const MediaSinkId& id() const { return sink_id_; }
   const std::string& name() const { return name_; }
 
   bool Equals(const MediaSink& other) const;
+  bool Empty() const;
 
  private:
-  const MediaSinkId sink_id_;
-  const std::string name_;
+  MediaSinkId sink_id_;
+  std::string name_;
 };
 
 }  // namespace media_router