Use bitwise operations instead of division, which is expensive on multiple CPU
architectures.

BUG=angleproject:956
TEST=angle_end2end_tests

Change-Id: I57ab540d447c03dae5a96bafb4975fc37e310261
Reviewed-on: https://chromium-review.googlesource.com/262181Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Nicolas Capens <capn@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>