Bug [WebKit]: Parent background-image renders two times

Created by: sbutkaliuk

Issue Summary

When using css background-image for parent node of mathjax formula this image renders twice in WebKit based browsers.

Steps to reproduce

Open jsfiddle example with webkit based browser (Chrome, Safari)

Bug screenshot (Chrome)

How it's supposed to look (Firefox):

Technical details

MathJax Version: v2.6-latest Browser: Any Webkit based (checked on Chrome and Safari) Output: at least HTML-CSS, SVG