Hide ES 3.0+ extensions from ES 2.0 clients Bug: angleproject:6928 Change-Id: I0aa1a9c124022fb7d89c2889b18817573ec271a8 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3404083 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Alexey Knyazev <lexa.knyazev@gmail.com>