gistfile1.js

exports.promptDirectorySelector = function promptDirectorySelector(worker) {
    console.debug("Opening directory selection dialog...");
    try { 
    var window = require("window/utils").getMostRecentBrowserWindow(); 
	  var fp = Cc["@mozilla.org/filepicker;1"].createInstance(Ci.nsIFilePicker);
	  fp.init(window, "Directory Selection", Ci.nsIFilePicker.modeGetFolder);
	  var result = fp.show();
	  if (result === Ci.nsIFilePicker.returnOK) {
        worker.postMessage({
                "command": "selectDirectory",
                "success": true,
				"content": fp.file.path
            });
	  }
    } catch(ex) {
        worker.postMessage({
                "command": "selectDirectory",
                "success": false    
            });
        console.error("Directory selection failed "+ex);
    } 
};