UniformsPerf: Properly limit maximum uniform vectors. The uniforms check was not correctly validating vector count instead of uniform count. Fix this, and reduce the maximum maxtrix uniforms to fix a crash on the perf bots. BUG=angleproject:1385 BUG=angleproject:1390 BUG=angleproject:1671 Change-Id: I261477c33639ed516ff6a29b38ab87f89309a7f1 Reviewed-on: https://chromium-review.googlesource.com/422533 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>