Add PRESUBMIT checks for not required testharness expected files.

This will prevent *-expected.txt files to be added when they are not
needed. It will prevent the test runner to do a file comparison when it
could simply check the output of the test.

BUG=None

Review URL: https://codereview.chromium.org/332583002

git-svn-id: svn://svn.chromium.org/blink/trunk@181313 bbb929c8-8fbe-4397-9dbb-9b2b20218538