[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_router.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_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_H_
+
+#include <string>
+#include <vector>
+
+#include "chrome/browser/media/router/media_route_id.h"
+#include "chrome/browser/media/router/media_sink.h"
+
+namespace media_router {
+
+class MediaRoute;
+class MediaRouteResponse;
+class MediaRoutesObserver;
+class MediaSource;
+class MediaSinksObserver;
+
+using MediaRouteResponseCallback =
+    base::Callback<void(const MediaRouteResponse&)>;
+
+// An interface for handling resources related to media routing.
+// Responsible for registering observers for receiving sink availability
+// updates, handling route requests/responses, and operating on routes (e.g.
+// posting messages or closing).
+class MediaRouter {
+ public:
+  virtual ~MediaRouter() {}
+
+  // Requests a media route from |source| to |sink_id|.
+  // |callback| is invoked with a response indicating success or failure.
+  // If it is not possible to request a route, returns kInvalidRouteRequestId.
+  // Otherwise a valid RouteRequestId will be returned, which can be used with
+  // |UnregisterMediaRouteResponseCallback()| if the caller no longer wants
+  // the callback invoked when a response comes back.
+  virtual RouteRequestId StartRouteRequest(
+      const MediaSource& source,
+      const MediaSinkId& sink_id,
+      const MediaRouteResponseCallback& callback) = 0;
+
+  // Unregisters a callback registered with a pending media route request,
+  // e.g., when the user has canceled presentation by closing the media router
+  // dialog.
+  // It does NOT cancel the route request, only the callback previously

[mark a. foltz, 2015/03/31 22:10:24]

Do we need an API to cancel a pending route request?  Could file this as a
TODO/task to sort out the implications.

[imcheng, 2015/04/01 00:55:16]

We could add one when we need it. I can file a feature request to make sure it's
discussed. We need to think about the possible use cases and if it's feasible
for the providers to implement such a feature.

+  // registered via |StartRouteRequest|.
+  // |request_id|: A valid request ID returned by |StartRouteRequest()|.
+  virtual void UnregisterMediaRouteResponseCallback(
+      const RouteRequestId& request_id) = 0;
+
+  // Closes the media route specified by |route_id|.
+  virtual void CloseRoute(const MediaRouteId& route_id) = 0;
+
+  // Registers |observer| with this MediaRouter. |observer| specifies a media
+  // source and will receive updates with media sinks that are compatible with
+  // that source. The initial update may happen synchronously.
+  // NOTE: This class does not assume ownership of |observer|. Callers must
+  // manage |observer| and make sure |UnregisterObserver()| is called
+  // before the observer is destroyed.
+  // Returns true if registration succeeded or the |observer| already exists.
+  // If the MRPM Host is not available, the registration request will fail
+  // immediately.
+  virtual bool RegisterObserver(MediaSinksObserver* observer) = 0;
+
+  // Unregisters |observer| from MediaRouter. |observer| will stop receiving
+  // further updates.
+  virtual void UnregisterObserver(MediaSinksObserver* observer) = 0;
+
+  // Posts |message| to a MediaSink connected via MediaRoute with |route_id|.
+  virtual void PostMessage(const MediaRouteId& route_id,
+                           const std::string& message) = 0;
+
+  // Adds a MediaRoutesObserver to listen for updates on MediaRoutes.
+  // The initial update may happen synchronously.
+  // MediaRouter does not own |observer|. |RemoveMediaRoutesObserver| should
+  // be called before |observer| is destroyed.
+  virtual void RegisterMediaRoutesObserver(MediaRoutesObserver* observer) = 0;
+
+  // Removes a previously added MediaRoutesObserver. |observer| will stop
+  // receiving further updates.
+  virtual void UnregisterMediaRoutesObserver(MediaRoutesObserver* observer) = 0;
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_H_