function requestFileSystemSuccess(fs) {
 fs.root.getFile('log.txt', {create: true}, function(fileEntry) {

    fileEntry.createWriter(function(fileWriter) {

      fileWriter.onwrite = function(e) {
        console.log('Write completed.');
      };

      fileWriter.onerror = function(e) {
        console.log('Write failed: ' + e.toString());
      };

      var bb = new window.WebKitBlobBuilder();
      bb.append('Lorem Ipsum');
      fileWriter.write(bb.getBlob('text/plain'));

    }, error);

  }, error);
}