ozone: Initialize a subsystem only if necessary.

ui/events/ozone/event_factory_ozone.h

Index: ui/events/ozone/event_factory_ozone.h
diff --git a/ui/events/ozone/event_factory_ozone.h b/ui/events/ozone/event_factory_ozone.h
index 888317a986ea3c0aeb605b8b77cdf8aeac141e31..d243761a6fff08d702f66b0316e06f83a380ba19 100644
--- a/ui/events/ozone/event_factory_ozone.h
+++ b/ui/events/ozone/event_factory_ozone.h
@@ -44,12 +44,9 @@ class EVENTS_OZONE_EXPORT EventFactoryOzone {
   virtual void WarpCursorTo(gfx::AcceleratedWidget widget,
                             const gfx::PointF& location);
 
-  // Returns the static instance last set using SetInstance().
+  // Returns the singleton instance.
   static EventFactoryOzone* GetInstance();
 
-  // Sets the implementation delegate. Ownership is retained by the caller.
-  static void SetInstance(EventFactoryOzone*);
-
  private:
   static EventFactoryOzone* impl_;  // not owned