Moves mash/wm into ash/mus

mash/wm/background_layout.h

-// 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.
-
-#ifndef MASH_WM_BACKGROUND_LAYOUT_H_
-#define MASH_WM_BACKGROUND_LAYOUT_H_
-
-#include "base/macros.h"
-#include "mash/wm/layout_manager.h"
-
-namespace mash {
-namespace wm {
-
-// Lays out the desktop background within background containers.
-class BackgroundLayout : public LayoutManager {
- public:
-  explicit BackgroundLayout(mus::Window* owner);
-  ~BackgroundLayout() override;
-
- private:
-  // Overridden from LayoutManager:
-  void LayoutWindow(mus::Window* window) override;
-
-  DISALLOW_COPY_AND_ASSIGN(BackgroundLayout);
-};
-
-}  // namespace wm
-}  // namespace mash
-
-#endif  // MASH_WM_BACKGROUND_LAYOUT_H_