add: flavourList["text/x-moz-url"] = { width: 2, iid: "nsISupportsWString" }; 
context:   getSupportedFlavours: function ()    {      var flavourList = { };      flavourList["application/x-moz-file"] = { width: 2, iid: "nsIFile" };      return flavourList;    }  
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/1287323a34b32e2d9336d559697e782c4ae05055/MsgComposeCommands.js/clean/mailnews/compose/resources/content/MsgComposeCommands.js