Fix allowing ES3 enum queries to call through to ES2 contexts. In some cases we would not validate the enums against the context version, allowing the app to call through to unimplemented features. BUG=angle:540 Change-Id: Ic89422a3a48882314c054f133961af0b4d8d739a Reviewed-on: https://chromium-review.googlesource.com/180970 Reviewed-by: Shannon Woods <shannonwoods@chromium.org> Reviewed-by: Nicolas Capens <nicolascapens@chromium.org> Commit-Queue: Nicolas Capens <nicolascapens@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>