add:   var dummy = gEM.datasource; 
context: function startupEM(){  // Make sure the update service is initialised.  var updateSvc = Components.classes["@mozilla.org/updates/update-service;1"]                            .getService(Components.interfaces.nsISupports);    gEM = Components.classes["@mozilla.org/extensions/manager;1"]                  .getService(Components.interfaces.nsIExtensionManager);    gEM.QueryInterface(Components.interfaces.nsIObserver);  gEM.observe(null, "app-startup", null);  gEM.observe(null, "profile-after-change", "startup");    var needsRestart = false;  try {    needsRestart = gEM.checkForMismatches();  }  catch (e) {    needsRestart = gEM.start(null);  }    if (needsRestart)    gEM.start(null);}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/10234/4ebe47cda63b0ddf56ff9c88394348a8c9f3983d/head_extensionmanager.js/clean/toolkit/mozapps/extensions/test/unit/head_extensionmanager.js