Makes ash/mus use RootWindowControllerCommon

ash/mus/background_layout.cc

Index: ash/mus/background_layout.cc
diff --git a/ash/mus/background_layout.cc b/ash/mus/background_layout.cc
deleted file mode 100644
index b6ecec9dc670f11cb0932a422b1bed7a61268fdb..0000000000000000000000000000000000000000
--- a/ash/mus/background_layout.cc
+++ /dev/null
@@ -1,25 +0,0 @@
-// 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 "ash/mus/background_layout.h"
-
-#include "components/mus/public/cpp/window.h"
-
-namespace ash {
-namespace mus {
-
-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 mus
-}  // namespace ash