Can step_timeout be used in reftests?

[foolip]

In #5543 the lint said:

apng/animated-png-timeout.html:7: setTimeout used; step_timeout should typically be used instead (SET TIMEOUT)

There was 1 error (SET TIMEOUT: 1)
You must fix all errors; for details on how to fix them, see
https://github.com/w3c/web-platform-tests/blob/master/docs/lint-tool.md

However, instead of fixing a particular error, it's sometimes
OK to add a line to the lint.whitelist file in the root of the
web-platform-tests directory to make the lint tool ignore it.

For example, to make the lint tool ignore all 'SET TIMEOUT'
errors in the apng/animated-png-timeout.html file,
you could add the following line to the lint.whitelist file.

SET TIMEOUT:apng/animated-png-timeout.html

However, step_timeout is a part of testharness.js and including that would be strange even if it did work. (Not tested.) I added the suggested line to lint.whitelist.

@gsnedders @jgraham

[gsnedders]

No, it can't be. But @jgraham's view was that it is worth linting for given the majority of tests are testharness.js tests, and we can't in general detect whether support files form part of a reftest or a testharness.js test. Except, like, this is a reftest and we can tell it is.

[foolip]

ci_lint.sh builds the manifest, but how is it used? Seems like it could be used for this.

[foolip]

This happened again in #6110 and I'll add that to the whitelist too. What would it take to just not do this check for reftests?