crosperf: fix lint warnings.

BUG=chromium:570454
TEST=crosperf_unittest.py is lint clean.

Change-Id: Ie33b95ec0cda61749b021e863ee65a47b491bb48
Reviewed-on: https://chrome-internal-review.googlesource.com/242520
Commit-Ready: Yunlian Jiang <yunlian@google.com>
Tested-by: Yunlian Jiang <yunlian@google.com>
Reviewed-by: Caroline Tice <cmtice@google.com>
1 file changed