In several places we weren't handling certain errors, or were
returning the wrong error code. Several dEQP negative API
tests are affected in functional.negative_api.texture.

BUG=angle:571

Change-Id: I19d7250aab2c15d709fd591b8df90ce883f9ac60
Reviewed-on: https://chromium-review.googlesource.com/201250Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>