HTML-CSS, FF32+, stretchy integral clipped

Something as simple as $$\int$$ gets clipped on the right, , e.g., on mathjax.org or using http://cdn.mathjax.org/mathjax/latest/test/sample-dynamic-2.html.

It happens at default and smaller zoom levels for me, disappears at larger zoom levels.

Seeing this on the develop branch as well.