In OpenGL parlance there are really only two color spaces:
Linear and SRGB. Vulkan is much more complicated with linear and
nonlinear SRGB, and multiple non-SRGB linear color spaces. Keep
things simple by working with OpenGL nomenclature.

Bug: angleproject:5176
Change-Id: Ia730a9a666a2b3325194b86dc588e7fd226c4183
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2483466
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>