Add media router common classes and unittests.

chrome/browser/media/router/media_router_defines.h

+// Copyright 2014 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_DEFINES_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_DEFINES_H_
+
+#include <string>
+
+#include "base/callback.h"
+
+namespace media_router {
+
+class MediaRouteResponse;
+
+typedef std::string MediaSinkId;

[mark a. foltz, 2015/02/26 01:11:22]

I would like to see a comment explaining the syntax of each of these and giving
an example value.

[mark a. foltz, 2015/02/26 01:11:22]

Replace typedefs with using-declarations.

https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/8dOAMzgR4ao

+
+typedef std::string MediaSource;

[mark a. foltz, 2015/02/26 01:11:22]

Mention that this is always a URI and I would be in favor of renaming to
MediaSourceUri.

+
+typedef base::Callback<void(const MediaRouteResponse&)>

[mark a. foltz, 2015/02/26 01:11:22]

I would put this at the end as it's not aliasing a simple type like the other
declarations.

+    MediaRouteResponseCallback;

[mark a. foltz, 2015/02/26 01:11:22]

Please verify this is really used in multiple headers before including it in the
common defines.

+typedef int64 RouteRequestId;

[mark a. foltz, 2015/02/26 01:11:22]

Add newlines consistently between entries (after comments are added).

+static const RouteRequestId kInvalidRouteRequestId = -1;
+
+typedef std::string MediaRouteId;
+
+typedef std::string IssueId;
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_DEFINES_H_