Obvious in hindsight. The problem wasn't that a signaling nan snuck
into the array, but that equality comparisons always return false if
either operand is a nan.

Bug: chromium:900133
Change-Id: I9cf82afd1ad1fcc3bf7138b612f615b1bd51b98a
Reviewed-on: https://chromium-review.googlesource.com/c/1309634Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57159}