问使用火狐的Downloads.jsm一次下载一个文件，同时观察它们？

EN

Task.spawn(function () {

  let list = yield Downloads.getList(Downloads.ALL);

  let view = {
    onDownloadAdded: download => console.log("Added", download),
    onDownloadChanged: download => console.log("Changed", download),
    onDownloadRemoved: download => console.log("Removed", download),
  };

  yield list.addView(view);
  try {
    let download = yield Downloads.createDownload({
      source: "http://www.mozilla.org/",
      target: OS.Path.join(OS.Constants.Path.tmpDir, "example-download.html"),
    });
    list.add(download);
    download.start();
  } finally {
    yield list.removeView(view);

    moveOnToNextDownload();
  }

}).then(null, Components.utils.reportError);