Moves mash/wm into ash/mus

mash/wm/background_layout.cc

-// 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.
-
-#include "mash/wm/background_layout.h"
-
-#include "components/mus/public/cpp/window.h"
-
-namespace mash {
-namespace wm {
-
-BackgroundLayout::BackgroundLayout(mus::Window* owner) : LayoutManager(owner) {}
-BackgroundLayout::~BackgroundLayout() {}
-
-// We explicitly don't make assertions about the number of children in this
-// layout as the number of children can vary when the application providing the
-// background restarts.
-
-void BackgroundLayout::LayoutWindow(mus::Window* window) {
-  window->SetBounds(gfx::Rect(owner()->bounds().size()));
-}
-
-}  // namespace wm
-}  // namespace mash