From: Anne van Kesteren [mailto:ann...@annevk.nl]
> Because it's very easy to move nodes from one tree to another and this > happens quite a bit through <iframe> and such. If the <iframe> then goes away > it would be a shame to have to leak it forever. This is all discussed to > great extent in the aforementioned bug. It's no more or less easy than moving normal JS objects from one realm to another, and we don't `__proto__`-munge those.
