It will default to on if ASSERT_ENABLED because we want testing to be done with the validation on. When needed, we can turn it off if we need to e.g. to de-clutter disassembly dumps while debugging.
Created attachment 401073 [details] proposed patch.
Thanks for the review. I added some details to the ChangeLog. Landed in r262570: <http://trac.webkit.org/r262570>.
<rdar://problem/63994958>