Optimize ValidateDrawStates. Apparently returning a small struct was slow enough to make a 2-3% difference in benchmark scores. Very visible on the MSVC sampling profiler. Bug: angleproject:2747 Change-Id: I459a127f3f2a0fc3a08db15c37257a67f63f20ce Reviewed-on: https://chromium-review.googlesource.com/1181465 Reviewed-by: Frank Henigman <fjhenigman@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>