Add textureOffset intrinsics to the symbol table. BUG=angle:541 Change-Id: Ied96edd073017a507369319a781b8ed23f60790b Reviewed-on: https://chromium-review.googlesource.com/181520 Tested-by: Nicolas Capens <nicolascapens@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org>