User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:42.0) Gecko/20100101 Firefox/42.0 Build ID: 20150704030210 Steps to reproduce: Make sure e10s is enabled. 1. Visit https://addons.mozilla.org/de/firefox/addon/hatsune-miku-yuki-ii-animat/ 2. Click Add to Firefox 3, Nothing happened (Obviously this doesn't work for any persona, but I like Miku so I use her as an example) Preview doesn't work either. Actual results: Nothing happened. Using a non e10s-window allows me to install a persona. Expected results: Apply the theme.