Add basic support for HLSL output of switch and case This patch outputs switch and case statements in HLSL, but ignores fall-through. Switch statements that include fall-through cause the platform HLSL compiler to generate errors. BUG=angle:921 Change-Id: I10efbfb45076cf4fd79840698abafd8111e597d4 Reviewed-on: https://chromium-review.googlesource.com/251527 Reviewed-by: Olli Etuaho <oetuaho@nvidia.com> Tested-by: Olli Etuaho <oetuaho@nvidia.com>