This is useful for determining if we are compiling to a D3D9 or D3D11
shader outside of the internal translator classes.

BUG=angle:656

Change-Id: Ib1c1d3de569edaa2b65c24c09d05aa4dd229d3e4
Reviewed-on: https://chromium-review.googlesource.com/201564Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>