nsIFrameLoader.sendCrossProcessKeyEvent is used to dispatch a key event to a remote browser. It has an optional aPreventDefault argument, which isn't used. That argument's value ends up getting accidentally passed as the value of nsContentUtils::SendKeyEvent's aAdditionalFlags argument: https://searchfox.org/mozilla-central/rev/7ed2a637dc305e90fed6ffb041c6b8fa162b66bd/dom/ipc/TabChild.cpp#2142-2143 The actual aPreventDefault argument for nsContentUtils::SendKeyEvent is the last one, but anyway is an outparam into which is stored whether preventDefault() was called on the event. Since it's unused, let's clean up this mess by removing the argument altogether. That lets us do some other simplifications, since nsIDOMWindowUtils.sendKeyEvent is also unused.

nsIDOMWindowUtils.sendKeyEvent is about to be removed. And I think the nsIFrameLoader variant too.

(In reply to Olli Pettay [:smaug] from comment #5) > nsIDOMWindowUtils.sendKeyEvent is about to be removed. Ah, I'm removing it too in the part 2 patch of this bug. :-) Feel free to dupe this bug against another one if it's already got patches for this.

I was thinking bug 1134542. Is there still more to do here?

No, that bug removes even more than I have here. I guess I must have forgotten / overlooked Masayuki's dev-platform mail about this!