Fix scanForWantedComponents not ignoring attribute values of 0. Slightly refactor scanForWantedComponents to not iterate over every attribute and only check the needed ones. BUG=angleproject:2069 Change-Id: I77bab7764552093f79472809aad3594be351831a Reviewed-on: https://chromium-review.googlesource.com/537132 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>