Follow-up to bug 673125. The patch in that bug adds a test (Frame-onStep-08.js) that basically says that if you set a breakpoint on every line of a script, onStep should still fire. I wrote the test, though, and I wasn't really thinking about it. That could be annoying API. I'm not sure there's a decision that will be good for all users. We should at least discuss it, though, make a deliberate choice, and document it.