code: function initWatchers(changeCallback, offlineCallback) {
          _changeCallback = changeCallback;
          _offlineCallback = offlineCallback;
  
          if (_isRunningOnWindowsXP && _offlineCallback) {
              _offlineCallback();
          }
      }
docs: Initialize file watching for this filesystem, using the supplied
  changeCallback to provide change notifications. The first parameter of
  changeCallback specifies the changed path (either a file or a directory);
  if this parameter is null, it indicates that the implementation cannot
  specify a particular changed path, and so the callers should consider all
  paths to have changed and to update their state accordingly. The second
  parameter to changeCallback is an optional FileSystemStats object that
  may be provided in case the changed path already exists and stats are
  readily available. The offlineCallback will be called in case watchers
  are no longer expected to function properly. All watched paths are
  cleared when the offlineCallback is called.
  
  @param {function(?string, FileSystemStats=)} changeCallback
  @param {function()=} offlineCallback