[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 "base/callback.h"
+#include "chrome/browser/media/router/media_route.h"
+#include "chrome/browser/media/router/media_route_id.h"
+#include "chrome/browser/media/router/media_sink.h"
+
+namespace media_router {
+
+class MediaRoutesObserver;
+class MediaSource;
+class MediaSinksObserver;
+
+// Type of callback used in |RequestRoute()|. Callback is invoked when the
+// route request either succeeded or failed.
+// The first argument is the route created. If the route request failed, this
+// will be a nullptr.
+// The second argument is the error string, which will be nonempty if the route
+// request failed.
+using MediaRouteResponseCallback =
+    base::Callback<void(scoped_ptr<MediaRoute>, const std::string&)>;
+
+// 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.
+  virtual void RequestRoute(const MediaSource& source,
+                            const MediaSinkId& sink_id,
+                            const MediaRouteResponseCallback& callback) = 0;
+
+  // Closes the media route specified by |route_id|.
+  virtual void CloseRoute(const MediaRouteId& route_id) = 0;
+
+  // Posts |message| to a MediaSink connected via MediaRoute with |route_id|.
+  // TODO(imcheng): Support additional data types: Blob, ArrayBuffer,
+  // ArrayBufferView.
+  virtual void PostMessage(const MediaRouteId& route_id,
+                           const std::string& message) = 0;
+
+  // Receives updates from a MediaRouter instance.
+  class Delegate {
+   public:
+    // Called when there is a message from a route.
+    // |route_id|: The route ID.
+    // |message|: The message.
+    virtual void OnMessage(const MediaRouteId& route_id,
+                           const std::string& message) = 0;
+  };
+
+ private:
+  friend class MediaSinksObserver;
+  friend class MediaRoutesObserver;
+
+  // The following APIs are called by MediaSinksObserver/MediaRoutesObserver
+  // only.
+
+  // 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.
+  // It is invalid to request the same observer more than once and will result
+  // in undefined behavior.
+  // If the MRPM Host is not available, the registration request will fail
+  // immediately.
+  virtual bool RegisterMediaSinksObserver(MediaSinksObserver* observer) = 0;

[Kevin Marshall, 2015/04/09 18:32:37]

Since these are pure virtual, did you intend to put these in a protected block?

[imcheng, 2015/04/09 18:44:27]

The intent is to let implementations of MediaRouter have access to these too, so
protected would make sense here. Changed the comment to reflect that as well.

+
+  // Removes a previously added MediaSinksObserver. |observer| will stop
+  // receiving further updates.
+  virtual void UnregisterMediaSinksObserver(MediaSinksObserver* observer) = 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 bool 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_