We were off by one varying, since D3D9 treats PSIZE specially.

BUG=angle:769

Change-Id: Id5242d12c3ca42da3f3f528ff4a21445dba89701
Reviewed-on: https://chromium-review.googlesource.com/221062Reviewed-by: Brandon Jones <bajones@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>