(Not for review) Dummy C++ side Custom Controls implementation

chrome/browser/media/router/media_router.h

Index: chrome/browser/media/router/media_router.h
diff --git a/chrome/browser/media/router/media_router.h b/chrome/browser/media/router/media_router.h
index 0f8fd4b7386f322a16b2950c04efea0b576f99e2..e58ea2cd9621b3161675184f41d44f0b77b8b872 100644
--- a/chrome/browser/media/router/media_router.h
+++ b/chrome/browser/media/router/media_router.h
@@ -33,6 +33,7 @@ class Origin;
 namespace media_router {
 
 class IssuesObserver;
+class MediaRouteController;
 class MediaRoutesObserver;
 class MediaSinksObserver;
 class PresentationConnectionStateObserver;
@@ -189,6 +190,12 @@ class MediaRouter : public KeyedService {
   // there is a change to the media routes, subclass MediaRoutesObserver.
   virtual std::vector<MediaRoute> GetCurrentRoutes() const = 0;
 
+  // Returns a nullptr if no MediaRoute exists for the given |route_id|, a
+  // connection with the extension-side controller could not be established,
+  // or on Android.
+  virtual MediaRouteController* GetControllerForRoute(
+      const MediaRoute::Id& route_id) = 0;
+
  private:
   friend class IssuesObserver;
   friend class MediaSinksObserver;