[webrtc-pc] RTCDataChannel.bufferedAmount value

lgrahl has just created a new issue for https://github.com/w3c/webrtc-pc:

== RTCDataChannel.bufferedAmount value ==
A discussion started in https://github.com/w3c/web-platform-tests/issues/10126 what the value of `.bufferedAmount` should report directly after a `.send` call. I believe @soareschen got the interpretation right that `.bufferedAmount` is not supposed to be updated before the task yielded back to the event loop (or however it's called in JS).

But I want to know whether there's a particular reason why it needs to be that way (other than it being easier to test). And if there is no functional requirement, then I would suggest removing that restriction. It may be a bit annoying to test but I wouldn't want to restrict implementations from sending as soon as possible.

Even if we decide against this, we should consider updating the description of `bufferedAmount` since a bunch of people misinterpreted that description, including me. Only after having read @soareschen's comment and the description a dozen of times, I was able to slowly comprehend it.

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/1823 using your GitHub account