[Media Router] Design MediaRouter interface with stub implementation.

chrome/browser/media/router/media_route_response.h

Index: chrome/browser/media/router/media_route_response.h
diff --git a/chrome/browser/media/router/media_route_response.h b/chrome/browser/media/router/media_route_response.h
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index 0000000000000000000000000000000000000000..6518cbc55a932844a74d7e14eee39cc1b30b1e42
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+++ b/chrome/browser/media/router/media_route_response.h
@@ -0,0 +1,57 @@
+// 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_ROUTE_RESPONSE_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTE_RESPONSE_H_
+
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/media/router/media_route.h"
+
+namespace media_router {
+
+// Response from the media route provider to a media route request.
+class MediaRouteResponse {
+ public:
+  // Creates a MediaRouteResponse object that indicates success.
+  // |request_id|: ID of original request.
+  // |route|: Route created.
+  static scoped_ptr<MediaRouteResponse> CreateFromSuccess(
+      const RouteRequestId& request_id,
+      const MediaRoute& route);
+
+  // Creates a MediaRouteResponse object that indicates failure.
+  // |request_id|: ID of original request.
+  // |error|: Failure reason.
+  static scoped_ptr<MediaRouteResponse> CreateFromError(
+      const RouteRequestId& request_id,
+      const std::string& error);

[xhwang, 2015/04/02 17:13:02]

There two functions are not used anywhere in this CL... I wonder why you need
scoped_ptr here. Can you just pass the const-ref over layers?

[imcheng, 2015/04/02 23:05:24]

I can upstream these factory functions in a later patch if you prefer. These are
scoped_ptrs because we have made MediaRouteResponses not
copy-constructable/assignable (we've added back scoped_ptr<MediaRoute> as one of
the members). But once they are constructed, we do pass them to function calls
using const-ref.

+
+  ~MediaRouteResponse();
+
+  const RouteRequestId& request_id() const { return request_id_; }
+
+  // Returns the route created, or an empty route if there was an error.
+  const MediaRoute& route() const { return route_; }
+
+  // Returns the error, or an empty string if the route was created
+  // successfully.
+  const std::string& error() const { return error_; }
+
+ private:
+  MediaRouteResponse(const RouteRequestId& request_id, const MediaRoute& route);
+  MediaRouteResponse(const RouteRequestId& request_id,
+                     const std::string& error);
+
+  // ID of original request. Set in all MediaRouteResponse objects, regardless
+  // of success/failure.
+  const RouteRequestId request_id_;
+  const MediaRoute route_;
+  const std::string error_;
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTE_RESPONSE_H_