Add a test for redefining an unavailable built-in This is going to guard against regressions when symbol table init is optimized. TEST=angle_unittests BUG=angleproject:2267 Change-Id: Iec7b9814f4af215dc0b3e8a39c8cfab004451836 Reviewed-on: https://chromium-review.googlesource.com/931883 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>