Revert to HLSL compiler optimization level 1 and work around a compiler bug with break in nested loops by using optimization level 3.

BUG=angle:603

Change-Id: Ib45815ef5bc3f72a3c51c7041c8a77ec573aa9e7
Reviewed-on: https://chromium-review.googlesource.com/194130Tested-by: Nicolas Capens <nicolascapens@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
(cherry picked from commit f3be8481)
Reviewed-on: https://chromium-review.googlesource.com/194109