[Media Router] Implement an internal Media Routes observer.

chrome/browser/media/router/media_router_factory.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_router_factory.h"
 
 #include "build/build_config.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
@@ skipping 51 matching lines @@
 MediaRouterFactory::~MediaRouterFactory() {
 }
 
 content::BrowserContext* MediaRouterFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }
 
 KeyedService* MediaRouterFactory::BuildServiceInstanceFor(
     BrowserContext* context) const {
+  MediaRouterBase* media_router = nullptr;
 #if defined(OS_ANDROID)
-  return new MediaRouterAndroid(context);
+  media_router = new MediaRouterAndroid(context);
 #else
-  return new MediaRouterMojoImpl(extensions::ProcessManager::Get(context));
+  media_router =
+      new MediaRouterMojoImpl(extensions::ProcessManager::Get(context));
 #endif
+  media_router->Initialize();
+  return media_router;
 }
 
 }  // namespace media_router