code: function(fileObj) {
    return new Promise(function (resolve, reject) {
      window.requestFileSystem(window.TEMPORARY, 4*1024*1024*1024,
          function({root}){
            resolve({root:root, fileObj: fileObj})
          },
          function(err) {
            reject(err)
          }
      );
    });
  }
docs: ------------------------- Chrome filesystem API(Promise wrapper)