cordova, access to local filesystem in browser platform

I trying to develop a cordova app to download file in local filesystem using browser platform but i have always problems with local storage uri. I using

...
// request access to file system
window.resolveLocalFileSystemURL(cordova.file.externalRootDirectory,

  function onFileSystemSuccess(fileSystem) {

    fileSystem.getFile(
      "test.txt", {create: true, exclusive: false},

      function onGetFileSuccess(fileEntry) {
         ...
      },

      function onGetFileError (error) {
      }
    );
  },

  function onFileSystemError(error) {
    ...
  }

);
...

i also used --disable-web-security --allow-file-access-from-files chromium args but i receive always errors on resolveLocalFileSystemURL also if i use other cordova.file.* values.