Move memory_coordinator_client and its registry to base/memory

components/memory_coordinator/common/client_registry.cc

Index: components/memory_coordinator/common/client_registry.cc
diff --git a/components/memory_coordinator/common/client_registry.cc b/components/memory_coordinator/common/client_registry.cc
deleted file mode 100644
index 57866c880d774fbfccf2638c484d3d64e3209989..0000000000000000000000000000000000000000
--- a/components/memory_coordinator/common/client_registry.cc
+++ /dev/null
@@ -1,21 +0,0 @@
-// 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.
-
-#include "components/memory_coordinator/common/client_registry.h"
-
-namespace memory_coordinator {
-
-ClientRegistry::ClientRegistry() : clients_(new ClientList) {}
-
-ClientRegistry::~ClientRegistry() {}
-
-void ClientRegistry::RegisterClient(MemoryCoordinatorClient* client) {
-  clients_->AddObserver(client);
-}
-
-void ClientRegistry::UnregisterClient(MemoryCoordinatorClient* client) {
-  clients_->RemoveObserver(client);
-}
-
-}  // namespace memory_coordinator