[Media Router] Implement JoinRoute + update CreateRoute API.

chrome/browser/ui/webui/media_router/media_router_webui_message_handler.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_webui_message_handler.h"
 
 #include "base/bind.h"
 #include "chrome/browser/ui/webui/media_router/media_router_ui.h"
 #include "chrome/grit/generated_resources.h"
 #include "content/public/browser/web_ui.h"
@@ skipping 157 matching lines @@
   initial_settings.SetString("headerText",
                              media_router_ui->GetInitialHeaderText());
 
   scoped_ptr<base::ListValue> sinks(SinksToValue(media_router_ui->sinks()));
   initial_settings.Set("sinks", sinks.release());
 
   scoped_ptr<base::ListValue> routes(RoutesToValue(media_router_ui->routes()));
   initial_settings.Set("routes", routes.release());
 
   scoped_ptr<base::ListValue> cast_modes(CastModesToValue(
-      media_router_ui->cast_modes(),
-      // TODO(imcheng): Use media_router_ui->source_host() once DEFAULT mode
-      // is upstreamed.
-      std::string()));
+      media_router_ui->cast_modes(), media_router_ui->GetFrameURLHost()));
   initial_settings.Set("castModes", cast_modes.release());
 
   web_ui()->CallJavascriptFunction(kSetInitialSettings, initial_settings);
   media_router_ui->UIInitialized();
 }
 
 void MediaRouterWebUIMessageHandler::OnCreateRoute(
     const base::ListValue* args) {
   std::string sink_id;
   int cast_mode_num;
@@ skipping 62 matching lines @@
 
 MediaRouterUI* MediaRouterWebUIMessageHandler::GetMediaRouterUI() const {
   MediaRouterUI* media_router_ui =
       static_cast<MediaRouterUI*>(web_ui()->GetController());
   DCHECK(media_router_ui);
   return media_router_ui;
 }
 
 }  // namespace media_router