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..37e271f62a8781d34e65c7f45029d310b3e0da68 100644
--- a/chrome/browser/ui/webui/media_router/media_router_ui.cc
+++ b/chrome/browser/ui/webui/media_router/media_router_ui.cc
@@ -135,29 +135,7 @@ MediaRouterUI::UIMediaRoutesObserver::~UIMediaRoutesObserver() {}
 void MediaRouterUI::UIMediaRoutesObserver::OnRoutesUpdated(
     const std::vector<MediaRoute>& routes,
     const std::vector<MediaRoute::Id>& joinable_route_ids) {
-  std::vector<MediaRoute> routes_for_display;
-  std::vector<MediaRoute::Id> joinable_route_ids_for_display;
-  for (const MediaRoute& route : routes) {
-    if (route.for_display()) {
-#ifndef NDEBUG
-      for (const MediaRoute& existing_route : routes_for_display) {
-        if (existing_route.media_sink_id() == route.media_sink_id()) {
-          DVLOG(2) << "Received another route for display with the same sink"
-                   << " id as an existing route. " << route.media_route_id()
-                   << " has the same sink id as "
-                   << existing_route.media_sink_id() << ".";
-        }
-      }
-#endif
-      if (base::ContainsValue(joinable_route_ids, route.media_route_id())) {
-        joinable_route_ids_for_display.push_back(route.media_route_id());
-      }
-
-      routes_for_display.push_back(route);
-    }
-  }
-
-  callback_.Run(routes_for_display, joinable_route_ids_for_display);
+  callback_.Run(routes, joinable_route_ids);
 }
 
 MediaRouterUI::MediaRouterUI(content::WebUI* web_ui)
@@ -297,7 +275,12 @@ void MediaRouterUI::InitCommon(content::WebContents* initiator) {
     query_result_manager_->SetSourcesForCastMode(MediaCastMode::TAB_MIRROR,
                                                  {mirroring_source}, origin);
   }
+
   UpdateCastModes();
+
+  // Get the current list of media routes, so that the WebUI will have routes
+  // information at initialization.
+  OnRoutesUpdated(router_->GetCurrentRoutes(), std::vector<MediaRoute::Id>());
 }
 
 void MediaRouterUI::InitForTest(
@@ -350,6 +333,25 @@ void MediaRouterUI::UpdateCastModes() {
   }
 }
 
+void MediaRouterUI::UpdateRoutesToCastModesMapping() {
+  std::unordered_map<MediaSource::Id, MediaCastMode> available_source_map;
+  for (const auto& cast_mode : cast_modes_) {
+    for (const auto& source :
+         query_result_manager_->GetSourcesForCastMode(cast_mode)) {
+      available_source_map.insert(std::make_pair(source.id(), cast_mode));
+    }
+  }
+
+  routes_and_cast_modes_.clear();
+  for (const auto& route : routes_) {
+    auto source_entry = available_source_map.find(route.media_source().id());
+    if (source_entry != available_source_map.end()) {
+      routes_and_cast_modes_.insert(
+          std::make_pair(route.media_route_id(), source_entry->second));
+    }
+  }
+}
+
 void MediaRouterUI::Close() {
   ConstrainedWebDialogDelegate* delegate = GetConstrainedDelegate();
   if (delegate) {
@@ -528,28 +530,33 @@ void MediaRouterUI::SetIssue(const Issue* issue) {
 void MediaRouterUI::OnRoutesUpdated(
     const std::vector<MediaRoute>& routes,
     const std::vector<MediaRoute::Id>& joinable_route_ids) {
-  routes_ = routes;
-  joinable_route_ids_ = joinable_route_ids;
+  routes_.clear();
+  joinable_route_ids_.clear();
 
-  std::unordered_map<MediaSource::Id, MediaCastMode> available_source_map;
-  for (const auto& cast_mode : cast_modes_) {
-    for (const auto& source :
-         query_result_manager_->GetSourcesForCastMode(cast_mode)) {
-      available_source_map.insert(std::make_pair(source.id(), cast_mode));
-    }
-  }
+  for (const MediaRoute& route : routes) {
+    if (route.for_display()) {
+#ifndef NDEBUG
+      for (const MediaRoute& existing_route : routes_) {
+        if (existing_route.media_sink_id() == route.media_sink_id()) {
+          DVLOG(2) << "Received another route for display with the same sink"
+                   << " id as an existing route. " << route.media_route_id()
+                   << " has the same sink id as "
+                   << existing_route.media_sink_id() << ".";
+        }
+      }
+#endif
+      if (base::ContainsValue(joinable_route_ids, route.media_route_id())) {
+        joinable_route_ids_.push_back(route.media_route_id());
+      }
 
-  current_cast_modes_.clear();
-  for (const auto& route : routes) {
-    auto source_entry = available_source_map.find(route.media_source().id());
-    if (source_entry != available_source_map.end()) {
-      current_cast_modes_.insert(
-          std::make_pair(route.media_route_id(), source_entry->second));
+      routes_.push_back(route);
     }
   }
+  UpdateRoutesToCastModesMapping();
 
   if (ui_initialized_)
-    handler_->UpdateRoutes(routes_, joinable_route_ids_, current_cast_modes_);
+    handler_->UpdateRoutes(routes_, joinable_route_ids_,
+                           routes_and_cast_modes_);
 }
 
 void MediaRouterUI::OnRouteResponseReceived(