Cu.importGlobalProperties(["File"]);

addMessageListener("file.open", function (e) {
  var testFile = Cc["@mozilla.org/file/directory_service;1"]
                   .getService(Ci.nsIDirectoryService)
                   .QueryInterface(Ci.nsIProperties)
                   .get("ProfD", Ci.nsIFile);
  testFile.append("prefs.js");

  File.createFromNsIFile(testFile).then(function(file) {
    sendAsyncMessage("file.opened", { file });
  });
});
