Workaround for Firefox 0S 2.0 which has getFeature(), not hasFeature() (bug 1097424)

https://bugzilla.mozilla.org/show_bug.cgi?id=1097424
I don't think we minify our yulelog assets...if that's the case, a shorter comment be better. something like:

    Only interested in three features below for now. Doing this for 2.0 where hasFeature doesn't exist.