jquery/jquery-ui — pull request #989 by christian314159 (2013-05-16 12:02:15+00:00)
Title: Resizable: Fixed sign error on offset calculation. Fixes #9307 Resizable...

Resizable: Fixed sign error on offset calculation. Fixes #9307 Resizable within scrolling container jump/can't be resized to containing element's width
http://jsfiddle.net/9XqG5/3/

I came across this issue today and worked out that once the the element that contains the resizables is scrolled too far and has a negative left value the woset variable. It will increase as a negative parent left offset is subtracted (and minus minus = plus). I fixed this with a simple Math.abs.