No-op glGenerateMipmap on zero-sized textures The spec says: > Otherwise, ... if any dimension is zero, all mipmap levels are left > unchanged. This is not an error. Bug: chromium:1220250 Change-Id: I45e007c1f8e9b80f405d3d096eb896a7246f7c8e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2979853 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>