This change refactors shaders to no longer be dependent on D3D-only concepts. BUG=angle:731 Change-Id: I1006112f1d31b7e41bd14bd3225ea157b7d6c6c9 Reviewed-on: https://chromium-review.googlesource.com/214467Tested-by: Brandon Jones <bajones@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>
