Add more test for GL_SRGB8 format And follow up changes from crrev.com/c/4819053 Bug: b/298037344 Change-Id: Ib27cc2fb8418d05d0b25f4abbdcf052d1f51c9ca Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4824046 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Charlie Lao <cclao@google.com>