Move memory_coordinator_client and its registry to base/memory

components/memory_coordinator/common/client_registry.h

-// Copyright 2016 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 COMPONENTS_MEMORY_COORDINATOR_COMMON_CLIENT_REGISTRY_H_
-#define COMPONENTS_MEMORY_COORDINATOR_COMMON_CLIENT_REGISTRY_H_
-
-#include "base/observer_list_threadsafe.h"
-#include "components/memory_coordinator/common/memory_coordinator_client.h"
-#include "components/memory_coordinator/common/memory_coordinator_export.h"
-
-namespace memory_coordinator {
-
-// ClientRegistry is a base class of process-specific memory coordinator
-// and provides ways to register/unregister MemoryCoordinatorClients.
-class MEMORY_COORDINATOR_EXPORT ClientRegistry {
- public:
-  ClientRegistry();
-  virtual ~ClientRegistry();
-
-  // Registers/unregisters a client. Does not take ownership of client.
-  void RegisterClient(MemoryCoordinatorClient* client);
-  void UnregisterClient(MemoryCoordinatorClient* client);
-
- protected:
-  using ClientList = base::ObserverListThreadSafe<MemoryCoordinatorClient>;
-  ClientList* clients() { return clients_.get(); }
-
- private:
-  scoped_refptr<ClientList> clients_;
-};
-
-}  // namespace memory_coordinator
-
-#endif  // COMPONENTS_MEMORY_COORDINATOR_COMMON_CLIENT_REGISTRY_H_