[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_router_impl.h

Index: chrome/browser/media/router/media_router_impl.h
diff --git a/chrome/browser/media/router/media_router_impl.h b/chrome/browser/media/router/media_router_impl.h
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+++ b/chrome/browser/media/router/media_router_impl.h
@@ -0,0 +1,100 @@
+// 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_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_IMPL_H_
+
+#include <map>
+#include <queue>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/containers/hash_tables.h"
+#include "base/gtest_prod_util.h"
+#include "base/macros.h"
+#include "base/memory/scoped_vector.h"
+#include "base/threading/thread_checker.h"
+#include "chrome/browser/media/router/media_route_provider_manager_host.h"
+#include "chrome/browser/media/router/media_router.h"
+#include "chrome/browser/media/router/media_sinks_observer.h"
+#include "components/keyed_service/core/keyed_service.h"
+
+namespace base {
+template <typename T>
+struct DefaultLazyInstanceTraits;
+}  // namespace base
+
+namespace media_router {
+
+class MediaRoute;
+class MediaRouterApiImpl;
+class MediaRoutesObserver;
+struct RoutesQueryResult;
+
+// Implementation of MediaRouter that delegates calls to
+// MediaRouteProviderManagerHost, which in turn handles communication
+// with the Media Route Provider Manager (MRPM) in the component extension.

[mark a. foltz, 2015/03/27 21:21:59]

I wouldn't mention the component extension here, since that is specific to the
type of MRPMH passed in by the caller.

[imcheng, 2015/03/30 22:49:10]

Done.

+// In addition, responses from MRPM are delegated to this class which then

[mark a. foltz, 2015/03/27 21:21:58]

s/MRPM/MediaRouteProviderManagerHost/

[imcheng, 2015/03/30 22:49:10]

Done.

+// invokes the observers / callbacks.
+// Instances of this class are created through MediaRouterImplFactory.

[mark a. foltz, 2015/03/27 21:21:58]

s/through/by/

Mention this is a profile-keyed service.

Discuss thread safety.

[imcheng, 2015/03/30 22:49:10]

Done.

+class MediaRouterImpl : public MediaRouter,
+                        public KeyedService,
+                        public MediaRouteProviderManagerHost::Delegate {
+ public:
+  ~MediaRouterImpl() override;
+
+  // |mrpm_host_| must be null at the time this is called.
+  // |mrpm_host| must not be null.
+  // Does not take ownership of |mrpm_host_|.
+  // This function can only be called once.
+  void SetMRPMHost(MediaRouteProviderManagerHost* mrpm_host);

[mark a. foltz, 2015/03/27 21:21:58]

Maybe this should just be Initialize()?

[imcheng, 2015/03/30 22:49:10]

Done.

+
+  // MediaRouter implementation.
+  RouteRequestId StartRouteRequest(
+      const MediaSource& source,
+      const MediaSinkId& sink_id,
+      const MediaRouteResponseCallback& callback) override;
+  void UnregisterMediaRouteResponseCallback(
+      const RouteRequestId& request_id) override;
+  void CloseRoute(const MediaRouteId& route_id) override;
+  bool RegisterObserver(MediaSinksObserver* observer) override;
+  void UnregisterObserver(MediaSinksObserver* observer) override;
+  void PostMessage(const MediaRouteId& route_id,
+                   const std::string& message,
+                   const std::string& extra_info_json) override;
+  void AddMediaRoutesObserver(MediaRoutesObserver* observer) override;
+  void RemoveMediaRoutesObserver(MediaRoutesObserver* observer) override;
+
+  // MediaRouteProviderManagerHost::Delegate implementation.
+  void OnMessage(const MediaRouteId& route_id,
+                 const std::string& message) override;
+  void OnSinksReceived(const MediaSource& source,
+                       const std::vector<MediaSink>& sinks) override;
+  void OnRouteResponseReceived(const RouteRequestId& request_id,
+                               const MediaRoute& route) override;
+  void OnRouteResponseError(const RouteRequestId& request_id,
+                            const std::string& error_text) override;
+  void OnRoutesUpdated(
+      const std::vector<MediaRoute>& routes,
+      const std::vector<MediaSink>& sinks) override;
+  void OnHostDestroyed(MediaRouteProviderManagerHost* host) override;
+
+ private:
+  friend class MediaRouterImplFactory;
+
+  // Use MediaRouterImplFactory::GetForBrowserContext().
+  MediaRouterImpl();
+
+  // MRPM host to forward calls to MRPM to.
+  // Responses from MRPM are also received from this host.
+  // Does not own this object.

[mark a. foltz, 2015/03/27 21:21:59]

I think you meant to say "Not owned by this object."

[imcheng, 2015/03/30 22:49:10]

Done.

+  MediaRouteProviderManagerHost* mrpm_host_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaRouterImpl);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_IMPL_H_