benchstat: add input from benchfmt.Results
benchstat: add input from benchfmt.Results

Change-Id: Idfc4d6b3cbd1e3c17182fe9565149e77ee1edb46
Reviewed-on: https://go-review.googlesource.com/35943
Reviewed-by: Quentin Smith <d6b8e48afb2534b213e391cab43016505747a234@golang.org>

golang/perf,golang/perf