Make ChecksumBench much more interesting and representative

Change-Id: I8573d050626949d4de462ba99eabef8398eb17f2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/700230
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Herb Derby <herb@google.com>
1 file changed