[Media Router] Convert to use typemaps for media_router.mojom.

chrome/browser/media/router/media_route.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/media/router/media_route.h"
 
 #include "base/logging.h"
 #include "chrome/browser/media/router/media_source.h"
 
 namespace media_router {
@@ skipping 10 matching lines @@
       media_sink_id_(media_sink_id),
       description_(description),
       is_local_(is_local),
       custom_controller_path_(custom_controller_path),
       for_display_(for_display),
       is_incognito_(false),
       is_offscreen_presentation_(false) {}
 
 MediaRoute::MediaRoute(const MediaRoute& other) = default;
 
+MediaRoute::MediaRoute() {}
 MediaRoute::~MediaRoute() = default;
 
 bool MediaRoute::Equals(const MediaRoute& other) const {
   return media_route_id_ == other.media_route_id_;
 }
 
 }  // namespace media_router