EnumSet hold a single integral field, hence it should be passed by
value. All users already do this, we are just inconsistent within the
declaration of EnumSet itself.

R=mlippautz@chromium.org

Change-Id: Ic2cac35fbd8fe3e98c1fe135bd334547dca30ab5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2071872Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66447}