Benchmark point sprites test with several varyings. A potential performance slowdown could be our geometry shader using extra logic in packing varyings. Test this by adding a variable number of varyings to the point sprites benchmark. Initial tests show it could slow down the test by about 30-40% or so, stil not catastrophic compared to D3D9. BUG=angle:705 Change-Id: Ia815f0ee28e2af2d3dc4d9f5675c27bbeb4cb119 Reviewed-on: https://chromium-review.googlesource.com/216468 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>