Revert of chromeos: Makes mushrome use simplified display management

ash/mus/ash_window_tree_host_mus.h

-// Copyright 2017 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_ASH_WINDOW_TREE_HOST_MUS_H_
-#define ASH_MUS_ASH_WINDOW_TREE_HOST_MUS_H_
-
-#include "ash/host/ash_window_tree_host.h"
-#include "ui/aura/mus/window_tree_host_mus.h"
-
-namespace ash {
-
-class TransformerHelper;
-
-// Implementation of AshWindowTreeHost for mus/mash.
-class AshWindowTreeHostMus : public AshWindowTreeHost,
-                             public aura::WindowTreeHostMus {
- public:
-  explicit AshWindowTreeHostMus(aura::WindowTreeHostMusInitParams init_params);
-  ~AshWindowTreeHostMus() override;
-
-  // AshWindowTreeHost:
-  void ToggleFullScreen() override;
-  bool ConfineCursorToRootWindow() override;
-  void UnConfineCursor() override;
-  void SetRootWindowTransformer(
-      std::unique_ptr<RootWindowTransformer> transformer) override;
-  gfx::Insets GetHostInsets() const override;
-  aura::WindowTreeHost* AsWindowTreeHost() override;
-  void PrepareForShutdown() override;
-  void RegisterMirroringHost(AshWindowTreeHost* mirroring_ash_host) override;
-
-  // aura::WindowTreeHostMus:
-  void SetRootTransform(const gfx::Transform& transform) override;
-  gfx::Transform GetRootTransform() const override;
-  gfx::Transform GetInverseRootTransform() const override;
-  void UpdateRootWindowSizeInPixels(
-      const gfx::Size& host_size_in_pixels) override;
-
- private:
-  std::unique_ptr<TransformerHelper> transformer_helper_;
-
-  DISALLOW_COPY_AND_ASSIGN(AshWindowTreeHostMus);
-};
-
-}  // namespace ash
-
-#endif  // ASH_MUS_ASH_WINDOW_TREE_HOST_MUS_H_