ProgressEvent.loaded references decompressed length, but total references the Content-Length header #403
Description
What is the issue with the XMLHttpRequest Standard?
(Continuing from #388.) When processing a response body, loaded on ProgressEvent is calculated after codings are handled in the Fetch specification, i. e. decompressed data size. However, total is unconditionally the result of extracting a length from the Content-Length header, which references compressed length when Content-Encoding is set to a known encoding. In those cases, the XHR specification should initialize length to zero. That would make lengthComputable false, which is the expected behavior for compressed responses.