Fix 'getDepth' in Texture::isLevelComplete. Was mistakenly inserted as getWidth in 691e58cd84360f. BUG=angle:681 Change-Id: Ibccf056dcb47c8711422efb8bd40fb6f64ff57d9 Reviewed-on: https://chromium-review.googlesource.com/244090 Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>