Technically more precise because something could be statically used
and never invoked. Also more consistent with the spec.

Bug: angleproject:5176
Change-Id: I70dd0787d67d9f046b7359abb24107cb430f5cae
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2483465
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>