Fix destruction order in mus_demo

services/ui/demo/mus_demo.cc

 // Copyright 2016 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 "services/ui/demo/mus_demo.h"
 
 #include "base/memory/ptr_util.h"
 #include "services/service_manager/public/cpp/connector.h"
 #include "services/ui/demo/window_tree_data.h"
 #include "services/ui/public/cpp/gpu/gpu.h"
 #include "ui/aura/client/default_capture_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/mus/property_converter.h"
 #include "ui/aura/mus/window_tree_client.h"
 #include "ui/aura/mus/window_tree_host_mus.h"
 #include "ui/aura/window.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/wm/core/wm_state.h"
 
 namespace ui {
 namespace demo {
 
 MusDemo::MusDemo() {}
 
 MusDemo::~MusDemo() {
   display::Screen::SetScreenInstance(nullptr);
+  // Destruction order is important here:
+  // WindowTreeClient must be destroyed before Env and WMState, otherwise
+  // segfault occurs as long as WindowTreeClient uses these singletons in it's
+  // dtor.

[kylechar, 2017/03/21 12:44:45]

s/dtor/destructor

+  window_tree_data_list_.clear();
+  window_tree_client_.reset();

[fwang, 2017/03/21 07:12:02]

Two points:
1) I think you should explain that windows (from window_tree_data_list_) must be
destroyed before the window tree client.
2) Maybe you can explicitly destroy Env and WMState to make things clearer.

[msisov, 2017/03/21 07:16:55]

Done.

 }
 
 void MusDemo::AddPrimaryDisplay(const display::Display& display) {
   screen_->display_list().AddDisplay(display,
                                      display::DisplayList::Type::PRIMARY);
 }
 
 bool MusDemo::HasPendingWindowTreeData() const {
   return !window_tree_data_list_.empty() &&
          !window_tree_data_list_.back()->IsInitialized();
@@ skipping 62 matching lines @@
 
 void MusDemo::OnPointerEventObserved(const PointerEvent& event,
                                      aura::Window* target) {}
 
 aura::PropertyConverter* MusDemo::GetPropertyConverter() {
   return property_converter_.get();
 }
 
 }  // namespace demo
 }  // namespace ui