Show Media Router toolbar icon ephemerally for MR dialogs

chrome/browser/media/router/media_router_ui_service.h

Index: chrome/browser/media/router/media_router_ui_service.h
diff --git a/chrome/browser/media/router/media_router_ui_service.h b/chrome/browser/media/router/media_router_ui_service.h
index 43b65107709183785d90895b2976b57e8e898878..3ca57fa44afe36fed1bfa1698a6b400355355e6d 100644
--- a/chrome/browser/media/router/media_router_ui_service.h
+++ b/chrome/browser/media/router/media_router_ui_service.h
@@ -23,10 +23,12 @@ class MediaRouterUIService : public KeyedService {
 
   static MediaRouterUIService* Get(Profile* profile);
 
+  virtual MediaRouterActionController* action_controller() const;
+
  private:
   friend class MediaRouterUIBrowserTest;
 
-  MediaRouterActionController action_controller_;
+  std::unique_ptr<MediaRouterActionController> action_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterUIService);
 };