Fix this by producing an error on undefined or negative shifts.

BUG=629518

Change-Id: Idfca5ed3fc8e557f6178408f3426a5ef2ce7cf14
Reviewed-on: https://chromium-review.googlesource.com/362020Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>