[Media Router] Add a supports_web_ui_controller attribute to MediaRoute

chrome/browser/ui/webui/media_router/media_router_webui_message_handler.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_WEBUI_MESSAGE_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_WEBUI_MESSAGE_HANDLER_H_
 
 #include <unordered_map>
 #include <vector>
 
@@ skipping 144 matching lines @@
   // used when updating sinks to determine if identity should be displayed.
   // Marked virtual for tests.
   virtual AccountInfo GetAccountInfo();
 
   // |true| if the associated Profile is incognito.
   bool incognito_;
 
   // Keeps track of whether a command to close the dialog has been issued.
   bool dialog_closing_;
 
+  // Whether the WebUI version of route controller is available for use.
+  const bool is_web_ui_route_controller_available_;
+
   // The media status currently shown in the UI.
   base::Optional<MediaStatus> current_media_status_;
 
   MediaRouterUI* media_router_ui_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterWebUIMessageHandler);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_WEBUI_MESSAGE_HANDLER_H_