[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_router_impl_factory.h

Index: chrome/browser/media/router/media_router_impl_factory.h
diff --git a/chrome/browser/media/router/media_router_impl_factory.h b/chrome/browser/media/router/media_router_impl_factory.h
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+// 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_IMPL_FACTORY_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_IMPL_FACTORY_H_
+
+#include "base/memory/singleton.h"
+#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
+
+namespace content {
+class BrowserContext;
+}  // namespace content
+
+namespace media_router {
+
+class MediaRouterImpl;
+
+// A factory that returns a MediaRouter object for a given BrowserContext,
+// creating one lazily if needed.
+class MediaRouterImplFactory : public BrowserContextKeyedServiceFactory {
+ public:
+  static MediaRouterImpl* GetMediaRouterForBrowserContext(
+      content::BrowserContext* context);
+  static MediaRouterImplFactory* GetInstance();
+
+ private:
+  friend struct DefaultSingletonTraits<MediaRouterImplFactory>;
+
+  MediaRouterImplFactory();
+  ~MediaRouterImplFactory() override;
+
+  // BrowserContextKeyedBaseFactory
+  KeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+  content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const override;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaRouterImplFactory);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_IMPL_FACTORY_H_