Cleanup from glBlitFramebuffer() 3D texture fix. Some minor refactoring. Move skips to test expectations and add a bug ID. Bug: angleproject:7291 Change-Id: I8d900a26508a28f6202a009c770cffb0e623dc5b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3638985 Commit-Queue: Stephen White <senorblanco@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>