Add support for layout(early_fragment_tests) in; Bug: angleproject:4314 Change-Id: I37b228f37201cc4188834e68459cd7294727c3ac Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2014240 Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>