add sample output to skpbench

Change-Id: I67338888313b11dceec1548e3e031cff92bf46f8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/364956
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
1 file changed