In constant folding of integer expressions this case is already being
handled.

BUG=angleproject:1599

Change-Id: Ifb3ea0279467f216e1c93909647b79fca24fcaf2
Reviewed-on: https://chromium-review.googlesource.com/406868
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>