Like Frame/FrameDestructionObserver, it would be nice to have PageDestructionObserver.
BTW, I've been thinking we should rename FrameDestructionObserver to FrameObserver, especially as it starts to observe more things.
Is anyone working on this? Otherwise, I can try to come up with the initial patch to take it forward...
We haven't found a case where this is necessary yet. We prefer to wait until we're sure we're going to need something before adding it.