ozone: Initialize a subsystem only if necessary.

ui/base/cursor/ozone/cursor_factory_ozone.h

Index: ui/base/cursor/ozone/cursor_factory_ozone.h
diff --git a/ui/base/cursor/ozone/cursor_factory_ozone.h b/ui/base/cursor/ozone/cursor_factory_ozone.h
index ac18a5010d08faeed940db3c74f7b9b7d71c8cff..23ac1132cfbc9f8b36dc93c83180ffd1bcfa02a4 100644
--- a/ui/base/cursor/ozone/cursor_factory_ozone.h
+++ b/ui/base/cursor/ozone/cursor_factory_ozone.h
@@ -16,12 +16,9 @@ class UI_BASE_EXPORT CursorFactoryOzone {
   CursorFactoryOzone();
   virtual ~CursorFactoryOzone();
 
-  // Returns the static instance.
+  // Returns the singleton instance.
   static CursorFactoryOzone* GetInstance();
 
-  // Sets the static instance. Ownership is retained by the caller.
-  static void SetInstance(CursorFactoryOzone* impl);
-
   // Return the default cursor of the specified type. The types are listed in
   // ui/base/cursor/cursor.h. Default cursors are managed by the implementation
   // and must live indefinitely; there's no way to know when to free them.