Texture attachments need to validate that the attached mip level is within
the [baseLevel,maxLevel] range and that the texture is complete if the
attached mip level is not the base level.

BUG=722684

Change-Id: I859766506b295638572b75a0e2e9fed168be047a
Reviewed-on: https://chromium-review.googlesource.com/506928Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>