Custom properties with 'var' in the value aren't applied

[robdodson]

ex: --my-font: 'Varela Round' will not be applied because of the word Var in Varela. @sorvell

[ebidel]

From http://stackoverflow.com/questions/33445674/how-to-get-google-fonts-to-work-in-polymer-1-1-web-component

[TimvdLippe]

Well that was an evening of edge-cases and testing, but I think I cracked it now. #2662 shows the reported fixed behaviour.

The multiple mentions are due to FireFox and Chrome parsing css selectors differently, but unrelated to the actual purpose of testing. Sorry for the spam.