Add media router common classes and unittests.

chrome/browser/media/router/route_id_manager.h

Index: chrome/browser/media/router/route_id_manager.h
diff --git a/chrome/browser/media/router/route_id_manager.h b/chrome/browser/media/router/route_id_manager.h
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+// 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_ROUTE_ID_MANAGER_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_ROUTE_ID_MANAGER_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/singleton.h"
+#include "base/threading/non_thread_safe.h"
+
+namespace media_router {
+
+class MediaRoute;
+
+// Shared singleton which coordinates the assignment of unique IDs to
+// MediaRoute objects.
+// Class is not threadsafe; IDs should be created on the same thread.
+class RouteIDManager : public base::NonThreadSafe {
+ public:
+  static RouteIDManager* GetInstance();
+
+  std::string ForLocalRoute();
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(RouteIDManagerTest, ForLocalRoute);
+  friend struct DefaultSingletonTraits<RouteIDManager>;
+
+  RouteIDManager();
+
+  // Monotonically increasing ID number.
+  uint64 next_local_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(RouteIDManager);
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_ROUTE_ID_MANAGER_H_