Wait till rendering thread completion before applying webfonts

So that the fontfamily values are always 'seen' by the webfonts jquery
plugin. Missing this was causing incorrect behavior -overriding the
fontfamiliy from css- in random cases.

The stylesheet ext.uls.webfonts.css define font family values for
interlanguge links and autonym class. This patch make sure that that
css values are read by jquery.webfonts while deciding which font to
apply. Autonym font is supposed to be used for them. If jquery.webfonts
does not read that these elements has a font family defined in css as
"'Autonym', sans-serif", it will attempt to apply fonts as per user
preference or default fonts based on lang attribute. That will cause
applying bigger fonts.

jquery.webfonts does not apply any fonts, if an element has explicit
font family value defined by inline css or by external style sheets.

Bug: 59958
Change-Id: I2da436caa618bc2318e20e3c0492a6bf1c03e162