in workbox-v4.3.1/workbox-streams.dev.js [26:39]
function _getReaderFromSource(source) {
if (source.body && source.body.getReader) {
return source.body.getReader();
}
if (source.getReader) {
return source.getReader();
} // TODO: This should be possible to do by constructing a ReadableStream, but
// I can't get it to work. As a hack, construct a new Response, and use the
// reader associated with its body.
return new Response(source).body.getReader();
}