As discussed in Bug 1291320, add logic to SETA to ensure certain jobs are NOT optimized out when specific source files are changed. i.e. If a test's source is changed, when that push lands don't let SETA optimize out the TC job that runs that specific test. I would suggest approaching this logic when we are refactoring SETA for manifest-based testing down the road.

YEah, this is a problem when we do wpt updates; it usually takes a few pushes to work out if it will stick because we are uselessly running mochitest jobs etc. but not running the jobs for the tests that were updated.

This would make sense to fix on a next re-write.