Disallow bit-shifting when the left operand is negative. BUG=648063 Change-Id: I82d9fbdaf8791a396dd71eeb57d93967ba5d65bf Reviewed-on: https://chromium-review.googlesource.com/387115 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>