Can you clarify this a little bit? What is wrong about the current behavior? This method is implemented the same way for worker and window, is it broken for window too? And what do you mean by 'just throw in'?

Oh if this is related to https://github.com/w3c/user-timing/issues/22 then I think that our implementation is on par with level 2 so the behavior matches the spec. And then we don't really need to measure the usage requested?

If usage is low enough, we'd like to throw an exception in this case.

Yeah, looks like Philip came to the same conclusion that this is fine.
Closing.