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

chrome/browser/media/router/mojo/media_route_controller.cc

 // Copyright 2017 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/media/router/mojo/media_route_controller.h"
 
 #include <utility>
 
 #include "chrome/browser/media/router/media_router.h"
 
 namespace media_router {
 
 MediaRouteController::Observer::Observer(
     scoped_refptr<MediaRouteController> controller)
     : controller_(std::move(controller)) {
   controller_->AddObserver(this);
 }
 
 MediaRouteController::Observer::~Observer() {
   if (controller_)
     controller_->RemoveObserver(this);
 }
 
+void MediaRouteController::Observer::CheckForMediaStatusUpdates() {
+  if (controller_ && controller_->current_media_status().has_value())
+    OnMediaStatusUpdated(controller_->current_media_status().value());
+}
+
 void MediaRouteController::Observer::InvalidateController() {
   controller_ = nullptr;
   OnControllerInvalidated();
 }
 
 void MediaRouteController::Observer::OnControllerInvalidated() {}
 
 MediaRouteController::MediaRouteController(
     const MediaRoute::Id& route_id,
     mojom::MediaControllerPtr mojo_media_controller,
@@ skipping 28 matching lines @@
   mojo_media_controller_->SetMute(mute);
 }
 
 void MediaRouteController::SetVolume(float volume) const {
   DCHECK(is_valid_);
   mojo_media_controller_->SetVolume(volume);
 }
 
 void MediaRouteController::OnMediaStatusUpdated(const MediaStatus& status) {
   DCHECK(is_valid_);
+  current_media_status_ = base::make_optional<MediaStatus>(MediaStatus(status));
   for (Observer& observer : observers_)
     observer.OnMediaStatusUpdated(status);
 }
 
 void MediaRouteController::Invalidate() {
   is_valid_ = false;
   binding_.Close();
   mojo_media_controller_.reset();
   for (Observer& observer : observers_)
     observer.InvalidateController();
@@ skipping 25 matching lines @@
   DCHECK(is_valid_);
   observers_.RemoveObserver(observer);
 }
 
 void MediaRouteController::OnMojoConnectionError() {
   media_router_->DetachRouteController(route_id_, this);
   Invalidate();
 }
 
 }  // namespace media_router