GL_SAMPLE_COVERAGE_VALUE is implemented by inserting gl_SampleMask writing logic to fragment shader. New test added: MultisampleTest.ContentPresevedAfterInterruption. - Skip on D3D11 (Bug: angleproject:4609) Bug: angleproject:2634 Change-Id: Ib44daf0baccc36ea320596d81713156047da059c Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2281783 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jonah Ryan-Davis <jonahr@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>
