code: function(name, root) {
      this.name = name;
      if (root) {
          this.root = new DirectoryEntry(root.name, root.fullPath, this, root.nativeURL);
      } else {
          this.root = new DirectoryEntry(this.name, '/', this);
      }
  }
docs: An interface representing a file system
  
  @constructor
  {DOMString} name the unique name of the file system (readonly)
  {DirectoryEntry} root directory of the file system (readonly)