Revert of Finish eliminating PlatformWindowMus

ui/views/mus/window_tree_host_mus.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 UI_VIEWS_MUS_WINDOW_TREE_HOST_MUS_H_
 #define UI_VIEWS_MUS_WINDOW_TREE_HOST_MUS_H_
 
 #include "base/macros.h"
 #include "ui/aura/window_tree_host_platform.h"
 #include "ui/views/mus/mus_export.h"
 
 class SkBitmap;
 
-namespace bitmap_uploader {
- class BitmapUploader;
-}
-
 namespace mus {
 class Window;
 }
 
 namespace shell {
 class Connector;
 }
 
-namespace ui {
-class ViewProp;
-}
-
 namespace views {
 
 class InputMethodMUS;
 class NativeWidgetMus;
 class PlatformWindowMus;
 
 class VIEWS_MUS_EXPORT WindowTreeHostMus : public aura::WindowTreeHostPlatform {
  public:
   WindowTreeHostMus(shell::Connector* connector,
                     NativeWidgetMus* native_widget,
                     mus::Window* window);
   ~WindowTreeHostMus() override;
 
+  PlatformWindowMus* platform_window();
+
  private:
   // aura::WindowTreeHostPlatform:
   void DispatchEvent(ui::Event* event) override;
   void OnClosed() override;
   void OnActivationChanged(bool active) override;
   void OnCloseRequest() override;
 
   NativeWidgetMus* native_widget_;
   std::unique_ptr<InputMethodMUS> input_method_;
 
-  // Bitmap management.
-  std::unique_ptr<bitmap_uploader::BitmapUploader> bitmap_uploader_;
-  std::unique_ptr<ui::ViewProp> prop_;
-
   DISALLOW_COPY_AND_ASSIGN(WindowTreeHostMus);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_WINDOW_TREE_HOST_MUS_H_