Revert of Finish eliminating PlatformWindowMus

blimp/engine/app/ui/blimp_window_tree_host.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 "blimp/engine/app/ui/blimp_window_tree_host.h"
 
 #include "base/memory/ptr_util.h"
-#include "ui/gfx/native_widget_types.h"
 #include "ui/platform_window/stub/stub_window.h"
 
 namespace blimp {
 namespace engine {
 
 BlimpWindowTreeHost::BlimpWindowTreeHost() : aura::WindowTreeHostPlatform() {
-  SetPlatformWindow(base::WrapUnique(
-      new ui::StubWindow(this, gfx::kNullAcceleratedWidget)));
+  SetPlatformWindow(base::WrapUnique(new ui::StubWindow(this)));
 }
 
 BlimpWindowTreeHost::~BlimpWindowTreeHost() {}
 
 void BlimpWindowTreeHost::OnAcceleratedWidgetAvailable(
     gfx::AcceleratedWidget widget,
     float device_pixel_ratio) {
   // Do nothing to avoid creating an output surface and gpu process.
 }
 
 }  // namespace engine
 }  // namespace blimp