Add GetCurrentRoutes() to MediaRouter API, ensure dialog has routes at init

chrome/browser/media/router/media_router_base.cc

Index: chrome/browser/media/router/media_router_base.cc
diff --git a/chrome/browser/media/router/media_router_base.cc b/chrome/browser/media/router/media_router_base.cc
index aeffeeb68f1ea8f91577ba65fd26563f66ab2648..821b346e406132185fb2f8aa23ae176bf9fe777c 100644
--- a/chrome/browser/media/router/media_router_base.cc
+++ b/chrome/browser/media/router/media_router_base.cc
@@ -27,6 +27,7 @@ class MediaRouterBase::InternalMediaRoutesObserver
   void OnRoutesUpdated(
       const std::vector<MediaRoute>& routes,
       const std::vector<MediaRoute::Id>& joinable_route_ids) override {
+    current_routes = routes;
     incognito_route_ids.clear();
     // TODO(crbug.com/611486): Have the MRPM pass a list of joinable route ids
     // via |joinable_route_ids|, and check here if it is non-empty.
@@ -38,6 +39,7 @@ class MediaRouterBase::InternalMediaRoutesObserver
   }
 
   bool has_route;
+  std::vector<MediaRoute> current_routes;
   std::vector<MediaRoute::Id> incognito_route_ids;
 
  private:
@@ -72,6 +74,10 @@ void MediaRouterBase::OnIncognitoProfileShutdown() {
     TerminateRoute(route_id);
 }
 
+std::vector<MediaRoute> MediaRouterBase::GetCurrentRoutes() const {
+  return internal_routes_observer_->current_routes;
+}
+
 MediaRouterBase::MediaRouterBase() : initialized_(false) {}
 
 // static