|arguments| should be iterable

[classilla]

https://bugzilla.mozilla.org/show_bug.cgi?id=1067049

[classilla]

Needs https://bugzilla.mozilla.org/show_bug.cgi?id=1235656 first

[classilla]

And then https://bugzilla.mozilla.org/show_bug.cgi?id=1263811

[classilla]

Looks like we already landed 1235656 as part of something else.