Use origin pad.y since it can change during Add().  Resolves issue #991.
Use origin pad.y since it can change during Add().  Resolves issue #991.

thomasjm/MathJax,thomasjm/MathJax,minrk/components-mathjax,anueshenxing/MathJax,cheerfulstoic/MathJax,jeremykenedy/MathJax,cben/MathJax,Ivanwangcy/MathJax,physikerwelt/MathJax,thomasjm/MathJax,minrk/mathjax-component,jinntrance/mathjax,thomasjm/MathJax,minrk/components-mathjax,anusornc/MathJax,GerHobbelt/MathJax,perseoq/MathJax,jeremykenedy/MathJax,anusornc/MathJax,ManrajGrover/MathJax,cben/MathJax,cheerfulstoic/MathJax,Ivanwangcy/MathJax,Edraak/MathJax,jinntrance/mathjax,dpvc/MathJax,nvp2211/MathJax,anueshenxing/MathJax,GerHobbelt/MathJax,wikimedia/MathJax,mcanthony/MathJax,minrk/mathjax-component,thomasjm/MathJax,mcanthony/MathJax,ManrajGrover/MathJax,perseoq/MathJax,Edraak/MathJax,nvp2211/MathJax