ozone: Initialize a subsystem only if necessary.

ui/views/widget/desktop_aura/desktop_screen_ozone.cc

Index: ui/views/widget/desktop_aura/desktop_screen_ozone.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_ozone.cc b/ui/views/widget/desktop_aura/desktop_screen_ozone.cc
index 6c551653167a9385af357b730f936a7eb372457c..9708ad88bfc191d841defd6794cdaeed9bb484cc 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_ozone.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_ozone.cc
@@ -4,13 +4,11 @@
 
 #include "ui/views/widget/desktop_aura/desktop_screen.h"
 
-#include "ui/ozone/ozone_platform.h"
 #include "ui/views/widget/desktop_aura/desktop_factory_ozone.h"
 
 namespace views {
 
 gfx::Screen* CreateDesktopScreen() {
-  ui::OzonePlatform::Initialize();
   return DesktopFactoryOzone::GetInstance()->CreateDesktopScreen();
 }