Add a perf test for scissored draw calls Bug: angleproject:4988 Change-Id: I59facc66aaa2af216d3a6c6ef1e4efa934a45cb8 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2506779 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>