Manually write overflow checks for glDraw* The usage of checked numerics showed has a big hotspot in ValidateDrawAttribs. BUG=angleproject:1671 BUG=chromium:674143 Change-Id: I96392e099b2257e465fb47e1c96f9aa1f54a89ba Reviewed-on: https://chromium-review.googlesource.com/422428 Commit-Queue: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>