This is a fully semantically preserving CL, it just moves code around a
bit to make the follow-up CL easier to review.

R=ahaas@chromium.org

Bug: v8:6600, v8:8423
Change-Id: I0de80b18faa3ae570894cbd8073c495a5731d255
Reviewed-on: https://chromium-review.googlesource.com/c/1396096Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58569}