[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_route.h

Index: chrome/browser/media/router/media_route.h
diff --git a/chrome/browser/media/router/media_route.h b/chrome/browser/media/router/media_route.h
index a8564f63d0449be3e7080ceed2bf795fcb69b8f7..dbc3151f26a3285d37d76e218c7719451684e898 100644
--- a/chrome/browser/media/router/media_route.h
+++ b/chrome/browser/media/router/media_route.h
@@ -18,8 +18,7 @@
 namespace media_router {
 
 using RouteRequestId = int64;
-
-class MediaRouteFactory;
+const RouteRequestId kInvalidRouteRequestId = -1;
 
 // For now, a simple transition graph: NEW -> CONNECTED -> CLOSED.
 enum MediaRouteState {
@@ -75,12 +74,12 @@ class MediaRoute {
   bool Equals(const MediaRoute& other) const;
 
  private:
-  const MediaRouteId media_route_id_;
-  const MediaSource media_source_;
-  const MediaSink media_sink_;
-  const std::string description_;
-  const bool is_local_;
-  const MediaRouteState state_;
+  MediaRouteId media_route_id_;
+  MediaSource media_source_;
+  MediaSink media_sink_;
+  std::string description_;
+  bool is_local_;
+  MediaRouteState state_;
 };
 
 }  // namespace media_router