This gets rid of a bunch of compiler warnings with MSVC.

Change-Id: I73440f0d203603fe39a2408d2b9cc647700aa5fc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1893334Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Michaël Zasso <mic.besace@gmail.com>
Cr-Commit-Position: refs/heads/master@{#64692}