Backed out changeset 6aaa835ae0eb (bug 1620630) for causing xpcshell failures...

  downloader.delete(RECORD);

  Assert.ok(!(await OS.File.exists(localFilePath)));

  Assert.ok(

    !(await OS.File.exists(

      OS.Path.join(OS.Constants.Path.localProfileDir, ...downloader.folders)

    ))

  );

  Assert.ok(!(await OS.File.exists(downloader.baseFolder)));

});

add_task(clear_state);

  let worker = new PromiseWorker.AbstractWorker();

  worker.dispatch = function(method, args = []) {

    let prefix = "OS.File " + method;

    performance.mark(prefix + "-start");

    try {

    return Agent[method](...args);

    } finally {

      let name = prefix;

      if (args.length && args[0].string) {

        // Including the path in the marker name here means it will be part of

        // profiles. It's fine to include personally identifiable information

        // in profiles, because when a profile is captured only the user will

        // see it, and before uploading it a sanitization step will be offered.

        // The 'OS.File ' prefix will help the profiler know that these marker

        // names should be sanitized.

        name += " — " + args[0].string;

      }

      performance.measure(name, prefix + "-start");

    }

  };

  worker.log = LOG;

  worker.postMessage = function(message, ...transfers) {