Summary:
Changelog: [iOS][Internal] - Implement screenX/screenY properties on the PointerEvent interface
This diff implements the screenX/screenY properties which report the position of a pointer in the device's physical screen coordinates.
Reviewed By: lunaleaps
Differential Revision: D37794415
fbshipit-source-id: 6c39c3651812f99e66b93647579a2935598ef6f2