We only assigned to elementIndex, and never referenced the value
at any point in our code.

BUG=angle:466

Change-Id: I541a353110bcd1863b07b21bcf21fad38be19ca1
Reviewed-on: https://chromium-review.googlesource.com/199735Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>