[Media Router] Notify MRUI of a media status update when it starts observing

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/media_router/media_router_ui.h"
 
 #include <algorithm>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ skipping 139 matching lines @@
 
 void MediaRouterUI::UIMediaRoutesObserver::OnRoutesUpdated(
     const std::vector<MediaRoute>& routes,
     const std::vector<MediaRoute::Id>& joinable_route_ids) {
   callback_.Run(routes, joinable_route_ids);
 }
 
 MediaRouterUI::UIMediaRouteControllerObserver::UIMediaRouteControllerObserver(
     MediaRouterUI* ui,
     scoped_refptr<MediaRouteController> controller)
-    : MediaRouteController::Observer(std::move(controller)), ui_(ui) {}
+    : MediaRouteController::Observer(std::move(controller)), ui_(ui) {
+  CheckForMediaStatusUpdates();

[mark a. foltz, 2017/05/12 21:00:58]

Instead you could call OnMediaStatusUpdated(controller->current_media_status()).

[takumif, 2017/05/12 22:20:58]

That would require current_media_status() to be public (and that's why I didn't
do so initially), but it does make things simpler. Done.

+}
+
 MediaRouterUI::UIMediaRouteControllerObserver::
     ~UIMediaRouteControllerObserver() {}
 
 void MediaRouterUI::UIMediaRouteControllerObserver::OnMediaStatusUpdated(
     const MediaStatus& status) {
   ui_->UpdateMediaRouteStatus(status);
 }
 
 void MediaRouterUI::UIMediaRouteControllerObserver::OnControllerInvalidated() {
   ui_->OnRouteControllerInvalidated();
@@ skipping 640 matching lines @@
 }
 
 std::string MediaRouterUI::GetSerializedInitiatorOrigin() const {
   url::Origin origin = initiator_
                            ? url::Origin(initiator_->GetLastCommittedURL())
                            : url::Origin();
   return origin.Serialize();
 }
 
 }  // namespace media_router