Additional run_perf_tests.py tweaks.

Additional run_perf_tests.py tweaks.
Committed: https://code.google.com/p/dart/source/detail?r=11995

[Emily Fortuna, 2012-09-06 01:17:34]

In the mayhem of committing and reverting my first DOM CL, this got accidentally
added to the "revert CL", and committed. I reverted it in the next CL but Pavel
had to make an additional change to Dartium, so he accidentally re-applied the
revert CL that had this extra file in here. This is basically cleaning up those
accidental commits. (I can explain the situation in person if this is
confusing).

[vsm, 2012-09-06 21:51:46]

lgtm