Add nondeterministic seed option for ProcessorOptimization test

BUG=skia:

Change-Id: Ie1dad1ab164eb36635095595e3200ae16e328832
Reviewed-on: https://skia-review.googlesource.com/9830
Reviewed-by: Eric Boren <borenet@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
4 files changed