Allow parallel creation of windows

services/ui/demo/window_tree_data.cc

 // 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.
 
 #include "services/ui/demo/window_tree_data.h"
 
 #include "base/time/time.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkColor.h"
@@ skipping 48 matching lines @@
 
 WindowTreeData::WindowTreeData(int square_size) : square_size_(square_size) {}
 
 WindowTreeData::~WindowTreeData() {}
 
 aura::Window* WindowTreeData::bitmap_window() {
   DCHECK(!window_tree_host_->window()->children().empty());
   return window_tree_host_->window()->children()[0];
 }
 
-void WindowTreeData::Init(
-    std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) {
-  if (window_tree_host) {
-    window_tree_host->InitHost();
-    window_tree_host->Show();
-    SetWindowTreeHost(std::move(window_tree_host));
-  }
+void WindowTreeData::Init() {
+  DCHECK(window_tree_host_);
+  DCHECK(!IsInitialized());
 
   // Initialize the window for the bitmap.
   window_delegate_ = new aura_extra::ImageWindowDelegate();
   aura::Window* root_window = window_tree_host_->window();
   aura::Window* bitmap_window = new aura::Window(window_delegate_);
   bitmap_window->Init(LAYER_TEXTURED);
   bitmap_window->SetBounds(gfx::Rect(root_window->bounds().size()));
   bitmap_window->Show();
   bitmap_window->SetName("Bitmap");
   root_window->AddChild(bitmap_window);
@@ skipping 27 matching lines @@
   gfx::ImageSkiaRep image_skia_rep(bitmap, 1);
   gfx::ImageSkia image_skia(image_skia_rep);
   gfx::Image image(image_skia);
 
   window_delegate_->SetImage(image);
   bitmap_window()->SchedulePaintInRect(gfx::Rect(bounds.size()));
 }
 
 }  // namespace demo
 }  // namespace ui