class ChromeFileBrowserHandler extends ChromeApi {
 static final JsObject _fileBrowserHandler = chrome['fileBrowserHandler'];

 ChromeFileBrowserHandler._();

 bool get available => _fileBrowserHandler != null;

 /**
  * Prompts user to select file path under which file should be saved. When the
  * file is selected, file access permission required to use the file (read,
  * write and create) are granted to the caller. The file will not actually get
  * created during the function call, so function caller must ensure its
  * existence before using it. The function has to be invoked with a user
  * gesture.
  * 
  * [selectionParams] Parameters that will be used while selecting the file.
  * 
  * Returns:
  * Result of the method.
  */
 Future<Map> selectFile(FileBrowserHandlerSelectFileParams selectionParams) {
   if (_fileBrowserHandler == null) _throwNotAvailable();

   var completer = new ChromeCompleter<Map>.oneArg(mapify);
   _fileBrowserHandler.callMethod('selectFile', [jsify(selectionParams), completer.callback]);
   return completer.future;
 }

 /**
  * Fired when file system action is executed from ChromeOS file browser.
  */
 Stream<OnExecuteEvent> get onExecute => _onExecute.stream;

 final ChromeStreamController<OnExecuteEvent> _onExecute =
     new ChromeStreamController<OnExecuteEvent>.twoArgs(_fileBrowserHandler, 'onExecute', _createOnExecuteEvent);

 void _throwNotAvailable() {
   throw new UnsupportedError("'chrome.fileBrowserHandler' is not available");
 }
}