Fix run_webkit_tests.py --lint-test-files after r175748

TBR=dpranke@chromium.org
BUG=369385

Review URL: https://codereview.chromium.org/319423002

git-svn-id: svn://svn.chromium.org/blink/trunk@175759 bbb929c8-8fbe-4397-9dbb-9b2b20218538