Correct an API test failure introduced by my changes in r240243.
My original patch was incrementing the pending callback count before deciding if a callback was actually needed. This left it out of balance, preventing the callback from ever firing.
Committed r240247: <https://trac.webkit.org/changeset/240247>
(In reply to Alexey Proskuryakov from comment #4)
> Yay tests!
And for actually paying attention to them! :-)
Committed r240308: <https://trac.webkit.org/changeset/240308>