The lack of error code was hiding errors in the Skia auto-roller.

Bug: skia:9812
Change-Id: Ib43e5eb1749161e9fa0186bfd4a293dadaf82f8a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2024178Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>