Backout patch for bug 380873 to see if it fixes the newly introduced leak (how ironic)

toolkit/components/passwordmgr/src/nsLoginManagerPrompter.js

@@ -397,11 +397,18 @@ var gModule = {
             contractID : "@mozilla.org/passwordmanager/authpromptfactory;1",
             className  : "LoginManagerPromptFactory",
             factory    : LoginManagerPromptFactory_Factory = {
+                singleton : null,
                 createInstance: function (aOuter, aIID) {
                     if (aOuter != null)
                         throw Components.results.NS_ERROR_NO_AGGREGATION;
 
-                    return new LoginManagerPromptFactory().QueryInterface(aIID);
+                    if (this.singleton == null) {
+                        var svc = new LoginManagerPromptFactory();
+                        this.singleton = svc;
+                    } else {
+                        svc = this.singleton;
+                    }
+                    return svc.QueryInterface(aIID);
                 }
             }
         }