GL: Work around Intel driver bug when clearing to zeros or ones. When clearing to zeros or ones on some Intel drivers on Mac, the clear color would be incorrect. This replicates the chromium clear_to_zero_or_one_broken workaround. BUG=angleproject:3672 Change-Id: I0f065420b577bd8f8d931ccdbeeebdcbf9fd08d2 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1692977 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>