This was a typo that never had any effect but it could cause problems in
Debug but in release border_pixel could have contain garbage and cause
an X11 error.

BUG=angleproject:892

Change-Id: Id6dc24c726730d998b419101239b3a43d6675330
Reviewed-on: https://chromium-review.googlesource.com/286251Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>