Summary:
This reverts D21285438 and patches some holes in the layout invalidation routines.
(I tried to use `didAddSubview:` and `willRemoveSubview:` but those are annoying for other reasons; for example, `willRemoveSubview:` can be called from within `dealloc` which is surprising. Also they still don't catch the case where subviews are being reordered.)
Reviewed By: Andrey-Mishanin
Differential Revision: D21512129
fbshipit-source-id: 1d9e8dac9333eddfae2309d446ef4de9e83220d6
82898b784e