Add a spy for retinaGravatar to fix up some warnings.
Review Request #7335 — Created May 25, 2015 and submitted
When running the js-tests, there are a bunch of console errors about gravatars.
This is happening because we don't have gravatar source images, and the
retinaGravatarcode is trying to parse "undefined?s=32", which doesn't make a
lot of sense. Because we don't actually care about this, I've spied out the
retinaGravatarcode and just escape hatched it.