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.

[mark a. foltz, 2015/03/05 16:58:41]

This is a static singleton that uses a non-threadsafe way to maintain the IDs. 
It should become bound to a thread on first instantiation and check that only
thread is used to access it with e.g. ThreadChecker.

I don't see a strong need now to make it thread safe unless there is something
I'm missing in the rest of the implementation.

[Kevin M, 2015/03/05 18:34:18]

Done.

+class MediaRouteFactory {
+ public:
+  static MediaRouteFactory* GetInstance();
+
+  // Returns 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,
+                    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_