Add media router common classes and unittests.

chrome/browser/media/router/media_route_factory.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_ROUTE_FACTORY_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTE_FACTORY_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/singleton.h"
+#include "chrome/browser/media/router/media_sink.h"
+#include "chrome/browser/media/router/media_source.h"
+
+namespace media_router {
+
+class MediaRoute;
+
+// Shared singleton which coordinates the assignment of unique IDs to
+// MediaRoute objects.
+class MediaRouteFactory {
+ public:
+  static MediaRouteFactory* GetInstance();
+
+  // Creates a MediaRoute object with a unique ID.
+  // |type|: Type of media route.
+  // |media_source|: Description of source of the route.
+  // |sink_id|: ID of the MediaSink of the route.
+  // |description|: Description of the route to be displayed.
+  // |is_local|: true if the route was created from this browser.
+  MediaRoute* Create(const MediaSource& media_source,

[imcheng, 2015/03/03 22:53:10]

I think the fact that this returns a dynamically allocated MediaRoute pointer
kind of strange. Because everywhere else in the media router code we pass these
immutable objects by const ref, and we can copy MediaRoute objects by copy
constructor / copy assignment anyways. So why not just return by value here.

[Kevin M, 2015/03/03 23:28:05]

Done.

[mark a. foltz, 2015/03/04 06:22:59]

Doesn't look that way from my diff.

[Kevin M, 2015/03/04 23:33:32]

I neglected to git cl upload. Sorry.

+                     const MediaSinkId& sink_id,
+                     const std::string& description,
+                     bool is_local);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(MediaRouteFactoryTest, Create);
+  friend struct DefaultSingletonTraits<MediaRouteFactory>;
+
+  MediaRouteFactory();
+
+  // Gets the next route ID.
+  std::string NextRouteId();
+
+  // Monotonically increasing ID number.
+  uint64 next_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaRouteFactory);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTE_FACTORY_H_