$ gotest -test.v -test.run=IndexRune -test.bench=.*
=== RUN  strings_test.TestIndexRune
--- PASS: strings_test.TestIndexRune (0.0 seconds)
PASS
strings_test.BenchmarkIndexRune	20000000   105 ns/op
strings_test.BenchmarkIndexByte	50000000    48 ns/op

R=rsc, dsymonds
CC=golang-dev
https://golang.org/cl/4267050