Fix bugged tokens marked as reserved/free in ES2. We had accidentally marked 'smoooth', 'centroid' and 'case' as reserved in ES2, when they are available as identifiers. Additionally 'sampler2DShadow' was marked as free, instead of reserved. BUG=angle:550 Change-Id: I33ec1b790ad5b4d9a6f4d2ea2e91cec1ca8e7320 Reviewed-on: https://chromium-review.googlesource.com/186970 Reviewed-by: Nicolas Capens <nicolascapens@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>