crosperf: fix lint for expeirment_factory.py

BUG=chromium:567921
TEST=the file passes lint checking.

Change-Id: I6d2187d11a51f4e87b5bbd8b905e285bb4ed2475
Reviewed-on: https://chrome-internal-review.googlesource.com/241465
Commit-Ready: Yunlian Jiang <yunlian@google.com>
Tested-by: Yunlian Jiang <yunlian@google.com>
Reviewed-by: Caroline Tice <cmtice@google.com>
1 file changed