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

chrome/browser/ui/webui/media_router/media_router_ui.cc

Index: chrome/browser/ui/webui/media_router/media_router_ui.cc
diff --git a/chrome/browser/ui/webui/media_router/media_router_ui.cc b/chrome/browser/ui/webui/media_router/media_router_ui.cc
index 3374fc27a4c5285c2972b246aa0fd5e50e5f571d..afa019443166ba0ca6a7f39db11bc3096b9a47e7 100644
--- a/chrome/browser/ui/webui/media_router/media_router_ui.cc
+++ b/chrome/browser/ui/webui/media_router/media_router_ui.cc
@@ -164,6 +164,7 @@ MediaRouterUI::MediaRouterUI(content::WebUI* web_ui)
     : ConstrainedWebDialogUI(web_ui),
       handler_(new MediaRouterWebUIMessageHandler(this)),
       ui_initialized_(false),
+      initial_routes_received_(false),
       current_route_request_id_(-1),
       route_request_counter_(0),
       initiator_(nullptr),
@@ -531,6 +532,9 @@ void MediaRouterUI::OnRoutesUpdated(
   routes_ = routes;
   joinable_route_ids_ = joinable_route_ids;
 
+  if (!initial_routes_received_)
+    initial_routes_received_ = true;
+
   std::unordered_map<MediaSource::Id, MediaCastMode> available_source_map;
   for (const auto& cast_mode : cast_modes_) {
     for (const auto& source :
@@ -672,6 +676,15 @@ const std::string& MediaRouterUI::GetRouteProviderExtensionId() const {
       ->media_route_provider_extension_id();
 }
 
+const std::vector<MediaRoute>& MediaRouterUI::GetRoutes() {
+  if (!initial_routes_received_) {
+    // OnRoutesUpdated() updates |routes_| with routes for display.
+    routes_observer_->OnRoutesUpdated(router_->GetCurrentRoutes(),

[imcheng, 2016/11/30 19:54:06]

This feels a bit strange. You are calling the observer so that it will call back
to MRUI to update |routes_|. It looks like what you can do instead is to call
GetCurrentRoutes() in InitCommon() to populate |routes_|. Then you don't need
this method and |initial_routes_received_|.

[mark a. foltz, 2016/11/30 23:52:10]

Will this be the same routes list as UIMediaRoutesObserver?

[takumif, 2016/12/01 00:51:13]

UIMediaRoutesObserver::OnRoutesUpdated() filters out non-display routes. We
could avoid passing the routes through UIMediaRoutesObserver by moving the
filtering functionality to MediaRouterUI::OnRoutesUpdated().

+                                      std::vector<MediaRoute::Id>());
+  }
+  return routes_;
+}
+
 void MediaRouterUI::SetUIInitializationTimer(const base::Time& start_time) {
   DCHECK(!start_time.is_null());
   start_time_ = start_time;