Allow parallel creation of windows

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"
@@ skipping 20 matching lines @@
                                      display::DisplayList::Type::PRIMARY);
 }
 
 bool MusDemo::HasPendingWindowTreeData() const {
   return !window_tree_data_list_.empty() &&
          !window_tree_data_list_.back()->IsInitialized();
 }
 
 void MusDemo::AppendWindowTreeData(
     std::unique_ptr<WindowTreeData> window_tree_data) {
-  DCHECK(!HasPendingWindowTreeData());
   window_tree_data_list_.push_back(std::move(window_tree_data));
 }
 
 void MusDemo::InitWindowTreeData(
     std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) {
   DCHECK(HasPendingWindowTreeData());
   window_tree_data_list_.back()->Init(std::move(window_tree_host));
 }
 
+void MusDemo::InitWindowTreeDataExternal(
+    aura::WindowTreeHostMus* window_tree_host) {
+  DCHECK(HasPendingWindowTreeData());
+  auto window_tree_data = FindWindowTreeData(window_tree_host);
+  (*window_tree_data)->Init(nullptr);
+}
+
 void MusDemo::RemoveWindowTreeData(aura::WindowTreeHostMus* window_tree_host) {
   DCHECK(window_tree_host);
+  auto window_tree_data = FindWindowTreeData(window_tree_host);
+  window_tree_data_list_.erase(window_tree_data);
+}
+
+std::vector<std::unique_ptr<WindowTreeData>>::iterator
+MusDemo::FindWindowTreeData(aura::WindowTreeHostMus* window_tree_host) {
   auto it =
       std::find_if(window_tree_data_list_.begin(), window_tree_data_list_.end(),
                    [window_tree_host](std::unique_ptr<WindowTreeData>& data) {
                      return data->WindowTreeHost() == window_tree_host;
                    });
   DCHECK(it != window_tree_data_list_.end());
-  window_tree_data_list_.erase(it);
+  return it;
 }
 
 void MusDemo::OnStart() {
   screen_ = base::MakeUnique<display::ScreenBase>();
   display::Screen::SetScreenInstance(screen_.get());
 
   env_ = aura::Env::CreateInstance(aura::Env::Mode::MUS);
   capture_client_ = base::MakeUnique<aura::client::DefaultCaptureClient>();
   property_converter_ = base::MakeUnique<aura::PropertyConverter>();
   wm_state_ = base::MakeUnique<::wm::WMState>();
@@ skipping 29 matching lines @@
 
 void MusDemo::OnPointerEventObserved(const PointerEvent& event,
                                      aura::Window* target) {}
 
 aura::PropertyConverter* MusDemo::GetPropertyConverter() {
   return property_converter_.get();
 }
 
 }  // namespace demo
 }  // namespace ui