Use pageXOffset instead of scrollX (#1631)
Use pageXOffset instead of scrollX (#1631)

`scrollX`/`scrollY` do not work on some browsers, using `pageXOffset`/`pageYOffset` instead: https://developer.mozilla.org/en-US/docs/Web/API/Window/scrollX#Notes
ianstormtaylor/slate,ashutoshrishi/slate,ianstormtaylor/slate,isubastiCadmus/slate