Fix angle_gles1_conformance_tests compilation in Chromium. BUG=angleproject:2303 Change-Id: If22dd174d2a7b50b1416fa760494e99bbc813985 Reviewed-on: https://chromium-review.googlesource.com/894839 Reviewed-by: Lingfeng Yang <lfy@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>