Add Media Router Mojo impl code.

chrome/browser/media/router/media_router_mojo_impl_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_MOJO_IMPL_FACTORY_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_MOJO_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

[Wez, 2015/05/20 23:37:50]

nit: No need for this since the namespace is teeny weeny

[imcheng (use chromium acct), 2015/05/21 19:28:52]

Done.

+
+namespace media_router {
+
+class MediaRouterMojoImpl;
+
+// A factory that lazily returns a MediaRouterMojoImpl object for a given
+// BrowserContext, creating one lazily if needed.

[Wez, 2015/05/20 23:37:50]

nit: Can you clean up this comment, plz? :)

[imcheng (use chromium acct), 2015/05/21 19:28:53]

Done.

+class MediaRouterMojoImplFactory : public BrowserContextKeyedServiceFactory {
+ public:
+  static MediaRouterMojoImpl* GetApiForBrowserContext(
+      content::BrowserContext* context);
+  static MediaRouterMojoImplFactory* GetInstance();

[Wez, 2015/05/20 23:37:50]

If there are no non-static methods on MediaRouterMojoImplFactory then why do we
need there to be an instance of it? And if we need an instance somewhere
internal, why do we need to expose it anywhere, since no-one can call it?

[imcheng (use chromium acct), 2015/05/21 19:28:52]

Removed this function and inlined it in GetApiForBrowserContext.

+
+ private:
+  friend struct DefaultSingletonTraits<MediaRouterMojoImplFactory>;
+
+  MediaRouterMojoImplFactory();
+  ~MediaRouterMojoImplFactory() override;
+
+  // BrowserContextKeyedBaseFactory

[Wez, 2015/05/20 23:37:50]

... interface.

[imcheng (use chromium acct), 2015/05/21 19:28:52]

Done.

+  KeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+  content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const override;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaRouterMojoImplFactory);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_MOJO_IMPL_FACTORY_H_