We don't invalidate the map of the global object anymore.

BUG=v8:5561

Change-Id: I006066e9b675dd3d118efc8d00687b97419c427b
Reviewed-on: https://chromium-review.googlesource.com/456417Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43906}