Implement broadcasting of gl_FragColor. Bug 19353282 Change-Id: I4319ad1836de36cc4b91b04ed226f925f82013ee Reviewed-on: https://swiftshader-review.googlesource.com/5145 Reviewed-by: Alexis Hétu <sugoi@google.com> Tested-by: Nicolas Capens <capn@google.com> Reviewed-by: Nicolas Capens <capn@google.com>