Run DM on all bots.

I figure there's a lot of special cases and exemptions we may need to steal
from run_tests and run_gm, but might as well for now try as vanilla as
possible.

BUG=skia:
R=borenet@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/395443002