Fix scoped structure references. We had neglected to reference scope bracket values when initially constructing the scoped struct name. Fixes the new WebGL test. BUG=angle:618 Change-Id: Ie78a8264c9e16c5a6574cecd662adbd5475d6495 Reviewed-on: https://chromium-review.googlesource.com/197252 Reviewed-by: Nicolas Capens <nicolascapens@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>