Created attachment 653610 [details] [diff] [review] Patch If the main thread freezes while we're in visibility:none, then we never create a layer, so we won't start the animation. This is no worse than what we do currently, but perhaps we should force a layer if there is a visibility animation.
Will do bug 784239 instead. Morphing this bug.
Created attachment 653632 [details] [diff] [review] Patch Clean up hunks.