The [[pending resume promises]] slot gets filled with promises from early calls to resume (before context is allowed to start).

However, as far as I can tell, the spec never says when these promises are resolved.

The steps for running a control message to resume an AudioContext either reject the promises or "clear" the list (why aren't the promises resolved first?). On top of that, I suspect that these promises need to be resolved when the context becomes allowed to start. In which case, this issue is similar to the comment I added to #2251: the spec does not explain what happens when context becomes allowed to start.