Without the explicit constexpr keyword, Clang seems to be able to treat
these methods as constexpr, whereas MSVC will not.

Bug: v8:11760
Change-Id: I9f6492f38fb50dcaf7a4f09da0bd79c0da6a50eb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2912916Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74791}