Fix missing texture target validations. We were missing this in a few places, and this was giving runtime errors in dEQP negative tests. BUG=angleproject:901 Change-Id: I9de5b055dcfe4ad5c13c800a31b4a0b424863bee Reviewed-on: https://chromium-review.googlesource.com/266888 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Brandon Jones <bajones@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>