[Media Router] Remove the extension ID getter from MRMojoImpl

chrome/browser/ui/webui/cast/cast_ui.cc

 // Copyright 2016 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/cast/cast_ui.h"
 
-#include "chrome/browser/media/router/media_router_factory.h"
-#include "chrome/browser/media/router/mojo/media_router_mojo_impl.h"
+#include "chrome/browser/media/router/event_page_request_manager.h"
+#include "chrome/browser/media/router/event_page_request_manager_factory.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/grit/browser_resources.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_ui.h"
 #include "content/public/browser/web_ui_data_source.h"
 
 CastUI::CastUI(content::WebUI* web_ui)
     : content::WebUIController(web_ui) {
   // Retrieve the ID of the component extension.
-  // TODO(crbug.com/597778): remove reference to MediaRouterMojoImpl.
-  auto* router = static_cast<media_router::MediaRouterMojoImpl*>(
-      media_router::MediaRouterFactory::GetApiForBrowserContext(
-          web_ui->GetWebContents()->GetBrowserContext()));
-  std::string extension_id = router->media_route_provider_extension_id();
+  auto* event_page_request_manager =
+      media_router::EventPageRequestManagerFactory::GetApiForBrowserContext(
+          web_ui->GetWebContents()->GetBrowserContext());
+  std::string extension_id =
+      event_page_request_manager->media_route_provider_extension_id();
 
   // Set up the chrome://cast data source and add required resources.
   content::WebUIDataSource* html_source =
       content::WebUIDataSource::Create(chrome::kChromeUICastHost);
 
   html_source->AddResourcePath("cast.css", IDR_CAST_CSS);
   html_source->AddResourcePath("cast.js", IDR_CAST_JS);
   html_source->AddResourcePath("cast_favicon.ico", IDR_CAST_FAVICON);
   html_source->AddString("extensionId", extension_id);
   html_source->SetJsonPath("strings.js");
   html_source->SetDefaultResource(IDR_CAST_HTML);
   html_source->OverrideContentSecurityPolicyObjectSrc("object-src * chrome:;");
 
   content::WebUIDataSource::Add(Profile::FromWebUI(web_ui), html_source);
 }
 
 CastUI::~CastUI() {
 }