This gets rid of the weakness hacks which were needed for remembering that maps
as handlers are weak, and other handles are strong.

BUG=v8:7308

Change-Id: I7fd3252ba67350803e2207dc12bbdf6abbae7e23
Reviewed-on: https://chromium-review.googlesource.com/1055449Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53151}