Default 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: I4f7985a5648f1b5f54d80554c21aced7fc1777c2
Reviewed-on: https://chromium-review.googlesource.com/194129Tested-by: Nicolas Capens <nicolascapens@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>