This was blocking compilation for any new texture builtin that used offsets.

Bug: angleproject:3622
Change-Id: I30b221741796b53f8e47e3aeeebfbde3f1976bd6
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1699062Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Cody Northrop <cnorthrop@google.com>