Allow parallel creation of windows

services/ui/demo/window_tree_data.h

 // 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.
 
 #ifndef SERVICES_UI_DEMO_WINDOW_TREE_DATA_H_
 #define SERVICES_UI_DEMO_WINDOW_TREE_DATA_H_
 
 #include "base/memory/ptr_util.h"
 #include "base/timer/timer.h"
 
 namespace aura {
 class Window;
 class WindowTreeHostMus;
 }  // namespace aura
 
 namespace aura_extra {
 class ImageWindowDelegate;
 }  // namespace aura_extra
 
 namespace ui {
 namespace demo {
 
 class WindowTreeData {
  public:
   explicit WindowTreeData(int square_size);
   ~WindowTreeData();
 
-  // Initializes the window tree host and start drawing frames.
-  void Init(std::unique_ptr<aura::WindowTreeHostMus> window_tree_host);
-  bool IsInitialized() const { return window_delegate_; }
+  // Initializes a window for bitmap and starts drawing frames.
+  void Init();
 
   const aura::WindowTreeHostMus* WindowTreeHost() const {
     return window_tree_host_.get();
   }
 
  protected:
   void SetWindowTreeHost(
       std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) {
     window_tree_host_ = std::move(window_tree_host);
   }
 
  private:
+  bool IsInitialized() const { return window_delegate_; }
+
   // Draws one frame, incrementing the rotation angle.
   void DrawFrame();
 
   // Helper function to retrieve the window to which we draw the bitmap.
   aura::Window* bitmap_window();
 
   // The Window tree host corresponding to this data.
   std::unique_ptr<aura::WindowTreeHostMus> window_tree_host_;
 
   // Destroys itself when the window gets destroyed.
   aura_extra::ImageWindowDelegate* window_delegate_ = nullptr;
 
   // Timer for calling DrawFrame().
   base::RepeatingTimer timer_;
 
   // Current rotation angle for drawing.
   double angle_ = 0.0;
 
   // Size in pixels of the square to draw.
   const int square_size_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTreeData);
 };
 
 }  // namespace demo
 }  // namespace ui
 
 #endif  // SERVICES_UI_DEMO_WINDOW_TREE_DATA_H_