platform-window: Add a PlatformWindowFactory for creating windows.

ui/aura/window_tree_host_ozone.h

Index: ui/aura/window_tree_host_ozone.h
diff --git a/ui/aura/window_tree_host_ozone.h b/ui/aura/window_tree_host_ozone.h
index 88736f335248e050ff0a1cf62b18b95bbb6c35ea..2d410aa72e70425693a61e0a5332ab0193e4c3b2 100644
--- a/ui/aura/window_tree_host_ozone.h
+++ b/ui/aura/window_tree_host_ozone.h
@@ -9,7 +9,7 @@
 #include "ui/aura/window_tree_host.h"
 #include "ui/events/event_source.h"
 #include "ui/gfx/rect.h"
-#include "ui/platform_window/platform_window_delegate.h"
+#include "ui/platform_window/types/platform_window_delegate.h"
 
 namespace ui {
 class PlatformWindow;
@@ -55,12 +55,12 @@ class AURA_EXPORT WindowTreeHostOzone : public WindowTreeHost,
   // ui::EventSource overrides.
   virtual ui::EventProcessor* GetEventProcessor() OVERRIDE;
 
-  // Platform-specific part of this WindowTreeHost.
-  scoped_ptr<ui::PlatformWindow> platform_window_;
-
   // The identifier used to create a compositing surface.
   gfx::AcceleratedWidget widget_;
 
+  // Platform-specific part of this WindowTreeHost.
+  scoped_ptr<ui::PlatformWindow> platform_window_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowTreeHostOzone);
 };