Makes ash/mus use RootWindowControllerCommon

ash/mus/container_ids.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 ASH_MUS_CONTAINER_IDS_H_
 #define ASH_MUS_CONTAINER_IDS_H_
 
 #include <stddef.h>
 
 namespace ash {
 namespace mojom {
 enum class Container;
 }
 
 namespace mus {
 // Id used when there is no corresponding ash container.
 const int kUnknownAshId = -1;
 
-// The set of containers that allow their children to be active.
-extern const mojom::Container kActivationContainers[];
+// The set of shell window ids that allow their children to be active. The ids
+// correspond to ids defined in ash/common/shell_window_ids.h.
+extern const int kActivationContainers[];
 
 // Number of kActivationContainers.
 extern const size_t kNumActivationContainers;
 
-// Converts window ids between ash (ash/common/shell_window_ids.h) and
-// mash.
-mojom::Container AshContainerToMashContainer(int shell_window_id);
-int MashContainerToAshContainer(mojom::Container container);
+// Converts a Container to a shell window ids (ash/common/shell_window_ids.h).
+int MashContainerToAshShellWindowId(mojom::Container container);
 
 }  // namespace mus
 }  // namespace ash
 
 #endif  // ASH_MUS_CONTAINER_IDS_H_