Summary: Add a convenience construction method for CSSNode. CSSNode node = CSSNode.Create( positionType: CSSPositionType.Absolute, wrap: CSSWrap.Wrap, position: new Spacing(top:6, right:4), margin: new Spacing(bottom:5, left:3)); Reviewed By: emilsjolander Differential Revision: D4193380 fbshipit-source-id: 30b917f64e92997355a76e3b11799883b86fb9de