Use new macros for defining bit fields.

Bug: v8:6470
Change-Id: Ie580ba7fc64f9958a3d4586d54d67e5dc66f1b53
Reviewed-on: https://chromium-review.googlesource.com/529824
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45867}