With our fix to huge buffer allocations, an extra check was preventing
pixel pack from running on the first try.

BUG=angle:511

Change-Id: Idabafe4e204ad3b7bf2010595dc455affe93dae0
Reviewed-on: https://chromium-review.googlesource.com/198825Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>