Download status

[kfix]

create an NSProgress for the download task and notify com.apple.DownloadFileFinished
https://chromium.googlesource.com/chromium/src.git/+/master/chrome/browser/download/download_status_updater_mac.mm
set the Quarantine xattrs too: https://codereview.chromium.org/220037/patch/6001/7001