Is WebAPI Body.json async? : `Body.json` [returns a promise][1]. 

Is this method asynchronous to avoid blocking on reading large inbound data streams? 

If this is correct, does it do something like `setTimeout(sampleStream, 0)` repeatedly until the end of the stream is found?


  [1]: https://developer.mozilla.org/en-US/docs/Web/API/Body/json