dEQP only covers this behaviour in ES2.0 tests and they fail when running with
an ES3.1 context.

BUG=angleproject:3425

Change-Id: I339b83901434da92ae6dd6273460b0725644cdf5
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1602177Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>