Check modulo values passed to GM.

Check modulo values passed to GM.

R=reed@google.com
Committed: https://code.google.com/p/skia/source/detail?r=6248

[bsalomon, 2012-11-01 17:48:03]

This helps my dumb cmd batch script.

[reed1, 2012-11-01 17:58:45]

lgtm