Some platform fontlist objects clear out the font cache when initializing fontlists but others (e.g. OSX) do not. Both the font and word caches should always be cleared when the fontlist is reinitialized.
Created attachment 8544989 [details] [diff] [review] patch, clear out font/word caches when initializing platform fontlists
Pushed to inbound: https://hg.mozilla.org/integration/mozilla-inbound/rev/e58ec2f295cc