This can be queried directly from the shader

Bug: b/124177079
Change-Id: I08aac7f77fb59f005295de3d417d24bf61fb3906
Reviewed-on: https://swiftshader-review.googlesource.com/c/24595Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>