[Media Router Tests] Add tests for MediaRouterFactory.

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 44 matching lines @@
           BrowserContextDependencyManager::GetInstance()) {
 #if !defined(OS_ANDROID)
   // On desktop platforms, MediaRouter depends on ProcessManager.
   DependsOn(extensions::ProcessManagerFactory::GetInstance());
 #endif
 }
 
 MediaRouterFactory::~MediaRouterFactory() {
 }
 
+// static
+MediaRouterFactory* MediaRouterFactory::GetMediaRouterFactoryForTest() {
+  return &service_factory.Get();
+}
+
 content::BrowserContext* MediaRouterFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }
 
 KeyedService* MediaRouterFactory::BuildServiceInstanceFor(
     BrowserContext* context) const {
 #if defined(OS_ANDROID)
   return new MediaRouterAndroid(context);
 #else
   return new MediaRouterMojoImpl(extensions::ProcessManager::Get(context));
 #endif
 }
 
 }  // namespace media_router