[Reland] [Media Router Tests] Add tests for MediaRouterFactory.

chrome/browser/media/router/media_router_factory.h

 // 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.
 
 #ifndef CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_FACTORY_H_
 #define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_FACTORY_H_
 
+#include "base/gtest_prod_util.h"
 #include "base/lazy_instance.h"
 #include "base/macros.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 namespace content {
 class BrowserContext;
 }
 
 namespace media_router {
 
 class MediaRouter;
 
 // A factory that lazily returns a MediaRouter implementation for a given
 // BrowserContext.
 class MediaRouterFactory : public BrowserContextKeyedServiceFactory {
  public:
   static MediaRouter* GetApiForBrowserContext(content::BrowserContext* context);
 
  protected:
   // We override the shutdown method for the factory to give the Media Router a
   // chance to remove off the record media routes.
   void BrowserContextShutdown(content::BrowserContext* context) override;
 
  private:
   friend struct base::DefaultLazyInstanceTraits<MediaRouterFactory>;
+  FRIEND_TEST_ALL_PREFIXES(MediaRouterFactoryTest,
+                           OffTheRecordBrowserContextShutdown);
 
   MediaRouterFactory();
   ~MediaRouterFactory() override;
 
+  // Exposed for testing.
+  static MediaRouterFactory* GetMediaRouterFactoryForTest();
+
   // BrowserContextKeyedServiceFactory interface.
   content::BrowserContext* GetBrowserContextToUse(
       content::BrowserContext* context) const override;
 
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterFactory);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_FACTORY_H_