Setup DiscardableMemory in the ash process

ui/views/mus/mus_client.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 UI_VIEWS_MUS_MUS_CLIENT_H_
 #define UI_VIEWS_MUS_MUS_CLIENT_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 12 matching lines @@
 class PropertyConverter;
 class Window;
 class WindowTreeClient;
 }
 
 namespace base {
 class SingleThreadTaskRunner;
 class Thread;
 }
 
-namespace discardable_memory {
-class ClientDiscardableSharedMemoryManager;
-}
-
 namespace service_manager {
 class Connector;
 }
 
 namespace wm {
 class WMState;
 }
 
 namespace views {
 
@@ skipping 107 matching lines @@
 
   std::unique_ptr<ScreenMus> screen_;
 
   std::unique_ptr<aura::PropertyConverter> property_converter_;
   std::unique_ptr<MusPropertyMirror> mus_property_mirror_;
 
   std::unique_ptr<aura::WindowTreeClient> window_tree_client_;
 
   std::unique_ptr<PointerWatcherEventRouter> pointer_watcher_event_router_;
 
-  std::unique_ptr<discardable_memory::ClientDiscardableSharedMemoryManager>
-      discardable_shared_memory_manager_;
-
   DISALLOW_COPY_AND_ASSIGN(MusClient);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_MUS_CLIENT_H_