Fix vertex array element limit condition. Certain overflows wouldn't be detected when the attribute size was less than the attribute size and we were drawing a small number of vertices. Fix this and also set the sentinel value for an integer overflow to be negative maxint instead of -1 to more effectily distinguish the cases. Bug: angleproject:1391 Change-Id: I970d5e2a630c0a84c2c02ac0ac41ab1a395819fe Reviewed-on: https://chromium-review.googlesource.com/1162264 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>