Add GLES1 conformance tests. BUG=angleproject:2303 Change-Id: I5955485e2392c573125bd8785ece103a9607f7d1 Reviewed-on: https://chromium-review.googlesource.com/867311 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Lingfeng Yang <lfy@google.com>