Turn shumway on and set Flash to CTP. Try to watch a video on youtube. The Flash object is deactivated, but there is no option in the urlbar to unblock it.
Last good revision: 711f08b0aa1d (2014-01-09) First bad revision: 37516445a0b5 (2014-01-10) Pushlog: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=711f08b0aa1d&tochange=37516445a0b5 Maybe because of bug 958110?
Confirmed, the video can no longer be activated.
Youtube switched to an html5-based player for Firefox, so it doesn't make sense to specifically look into this case anymore.