[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/extension_media_route_provider_manager_host.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_EXTENSION_MEDIA_ROUTE_PROVIDER_MANAGER_HOST_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_EXTENSION_MEDIA_ROUTE_PROVIDER_MANAGER_HOST_H_
+
+#include <string>
+
+#include "base/macros.h"
+#include "chrome/browser/media/router/media_route_provider_manager_host.h"
+#include "components/keyed_service/core/keyed_service.h"
+
+namespace content {
+class BrowserContext;
+}  // namespace content
+
+namespace media_router {
+
+// MediaRouteProviderManagerHost implementation that sits between

[Kevin M, 2015/03/26 20:50:14]

I think that this might be diving into the details too quickly. Bubble up the
most salient point to the top, which IMO would be a sentence like this

"This class encapsulates logic for reactivating the event page and queueing of
requests to be executed once event page is reactivated"

[imcheng, 2015/03/26 23:33:12]

Ok, I will just replace the entire comment block with that.

+// the Media Router and MediaRouterApiImpl (another MRPMH implementation).
+// This class serves the following purposes:
+// - Accepts Media Router related requests that needs to be forwarded to MRPM.
+//   Thus this class implements MediaRouteProviderManagerHost.
+// - Retains ownership of MediaRouterApiImpl, a MediaRouteProviderManagerHost
+//   implementation that talks to an event-page based MRPM component extension.
+//   This class encapsulates logic for reactivating the event page and queueing
+//   of requests to be executed once event page is reactivated. These logic are
+//   isolated from the Media Router as they are event page implementation
+//   details and should be transparent to Media Router.
+// - Relays data from MediaRouterApiImpl back to the Media Router, hence it
+//   implements MediaRouteProviderManagerHost::Delegate.

[Kevin M, 2015/03/26 20:50:14]

Still applicable?

[imcheng, 2015/03/26 23:33:12]

Removed.

+//   See MediaRouterApiImpl for more information.
+// TODO(imcheng): Define MediaRouterApiImpl.
+class ExtensionMediaRouteProviderManagerHost
+    : public MediaRouteProviderManagerHost,
+      public KeyedService {
+ public:
+  ~ExtensionMediaRouteProviderManagerHost() override;
+
+  // MediaRouteProviderManagerHost
+  void AddMediaSinksQuery(const MediaSource& source) override;
+  void RemoveMediaSinksQuery(const MediaSource& source) override;
+  void RequestRoute(const RouteRequestId& request_id,
+                    const MediaSource& source,
+                    const MediaSinkId& sink_id) override;
+  void CloseRoute(const MediaRouteId& route_id) override;
+  void PostMessage(const MediaRouteId& route_id,
+                   const std::string& message,
+                   const std::string& extra_info_json) override;
+  void StartMediaRoutesQuery() override;
+  void StopMediaRoutesQuery() override;
+
+ private:
+  friend class ExtensionMRPMHostFactory;
+
+  // Private ctor. To instantiate, call
+  // ExtensionMRPMHostFactory::GetMRPMHostForBrowserContext.
+  explicit ExtensionMediaRouteProviderManagerHost(
+      content::BrowserContext* context,
+      MediaRouteProviderManagerHost::Delegate* delegate);
+
+  // Delegate to forward MRPM responses to.

[Kevin M, 2015/03/26 20:50:14]

Delegate to receive MRPM responses?

[imcheng, 2015/03/26 23:33:12]

Done.

+  // Does not own this object.
+  MediaRouteProviderManagerHost::Delegate* delegate_;
+
+  // BrowserContext associated with this instance.
+  content::BrowserContext* context_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtensionMediaRouteProviderManagerHost);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_EXTENSION_MEDIA_ROUTE_PROVIDER_MANAGER_HOST_H_