Re: [fetch] Service worker request body reads need to invoke callbacks (#87)

Example code:

```
var r = new Request(url, { method: 'POST', body: myStream });
fetch(r);

// intercepted in service worker as
addEventListener('fetch', function(evt) {
  var req2 = new Request(evt.request, { body: evt.request.body.pipeThrough(transform) }); 
  return fetch(req2);
});
```

So we have two fetch() calls here; the intercepted fetch and the sw fetch.

I would expect the intercepted fetch to report upload progress when its Request.body is read.  So in this case, when the .pipeThrough() reads chunks from it.

How do we plan on reporting back upload progress?  Are we adding a callback to fetch() somewhere?

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/87#issuecomment-124554422