Add media router common classes and unittests.

chrome/browser/media/router/route_id_manager.cc

+// 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.
+
+#include "chrome/browser/media/router/route_id_manager.h"
+
+#include "base/memory/singleton.h"
+#include "base/strings/string_number_conversions.h"
+#include "chrome/browser/media/router/media_route.h"
+
+namespace media_router {
+
+const char kLocalRoutePrefix[] = "route-local-";
+
+RouteIDManager::RouteIDManager() : next_local_id_(0) {}
+
+std::string RouteIDManager::ForLocalRoute() {
+  DCHECK(CalledOnValidThread());
+  return kLocalRoutePrefix + base::Uint64ToString(next_local_id_++);
+}
+
+// static
+RouteIDManager* RouteIDManager::GetInstance() {
+  return Singleton<RouteIDManager>::get();
+}
+
+}  // namespace media_router