Fix GetShaderPrecisionFormat to return correct values on DX11 The integer precision is different on DirectX 9 and 11 backends. DirectX 11 guarantees native 32-bit integers. BUG=angle:919 Change-Id: I7619e66f8aaa1177c32b6da185fe805ce8a19b71 Reviewed-on: https://chromium-review.googlesource.com/250280 Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Olli Etuaho <oetuaho@nvidia.com>