choosing of application object

 let Application = Cc["@mozilla.org/fuel/application;1"] ? /* Firefox 3 */                    Cc["@mozilla.org/fuel/application;1"]                    .getService(Ci.fuelIApplication) :                   Cc["@mozilla.org/steel/application;1"] ? /* Thunderbird 3 */                    Cc["@mozilla.org/steel/application;1"]                   .getService(Ci.steelIApplication) :                   Cc["@mozilla.org/smile/application;1"] ? /*  SeaMonkey 2 */                   Cc["@mozilla.org/smile/application;1"]                   .getService(Ci.smileIApplication);