Demonstrate external-window-mode in mus-demo

services/ui/demo/mus_demo.h

Index: services/ui/demo/mus_demo.h
diff --git a/services/ui/demo/mus_demo.h b/services/ui/demo/mus_demo.h
index 941b2387be42874fd4287f2006f32215ba625cf4..5d7a19c029d9a20b0bb7ef527e22fd0e187adb37 100644
--- a/services/ui/demo/mus_demo.h
+++ b/services/ui/demo/mus_demo.h
@@ -17,6 +17,7 @@
 #include "services/service_manager/public/cpp/service.h"
 #include "services/ui/public/cpp/window_manager_delegate.h"
 #include "services/ui/public/cpp/window_tree_client_delegate.h"
+#include "services/ui/public/interfaces/window_tree_host.mojom.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/display/screen_base.h"
 
@@ -37,6 +38,8 @@ class MusDemo : public service_manager::Service,
   ~MusDemo() override;
 
  private:
+  struct WindowTreeData;
+
   // service_manager::Service:
   void OnStart() override;
   bool OnConnect(const service_manager::ServiceInfo& remote_info,
@@ -69,33 +72,24 @@ class MusDemo : public service_manager::Service,
                            const base::Callback<void(bool)>& on_done) override;
   void OnWmCancelMoveLoop(Window* window) override;
 
-  // Allocate a bitmap the same size as the window to draw into.
-  void AllocBitmap();
+  // Creates a new WindowTreeHost and adds its context to |window_tree_datas_|.
+  void AddWindowTreeHost();
+
+  // Sets up a timer to regularly draw frames to |window|.
+  void BeginDrawingFrames(Window* window);
 
   // Draws one frame, incrementing the rotation angle.
-  void DrawFrame();
+  void DrawFrame(WindowTreeData* data);
+
+  bool external_window_mode_;
 
-  Window* window_ = nullptr;
-  std::unique_ptr<WindowTreeClient> window_tree_client_;
   std::unique_ptr<GpuService> gpu_service_;
 
   // Dummy screen required to be the screen instance.
   std::unique_ptr<display::ScreenBase> screen_;
 
-  // Used to send frames to mus.
-  std::unique_ptr<BitmapUploader> uploader_;
-
-  // Bitmap that is the same size as our client window area.
-  SkBitmap bitmap_;
-
-  // Timer for calling DrawFrame().
-  base::RepeatingTimer timer_;
-
-  // Current rotation angle for drawing.
-  double angle_ = 0.0;
-
-  // Last time a frame was drawn.
-  base::TimeTicks last_draw_frame_time_;
+  // One WindowTreeData for each WindowTreeHost.
+  std::vector<std::unique_ptr<WindowTreeData>> window_tree_datas_;
 
   DISALLOW_COPY_AND_ASSIGN(MusDemo);
 };