diff --git a/browser/components/feeds/src/FeedWriter.js b/browser/components/feeds/src/FeedWriter.js
index ffa24840794..4f4040cad5e 100644
--- a/browser/components/feeds/src/FeedWriter.js
+++ b/browser/components/feeds/src/FeedWriter.js
@@ -47,6 +47,9 @@ const Cu = Components.utils;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
+const FEEDWRITER_CID = Components.ID("{49bb6593-3aff-4eb3-a068-2712c28bd58e}");
+const FEEDWRITER_CONTRACTID = "@mozilla.org/browser/feeds/result-writer;1";
+
 function LOG(str) {
   var prefB = Cc["@mozilla.org/preferences-service;1"].
               getService(Ci.nsIPrefBranch);
@@ -1377,17 +1380,12 @@ FeedWriter.prototype = {
       });
   },
 
-  // nsIClassInfo
-  getInterfaces: function FW_getInterfaces(countRef) {
-    var interfaces = [Ci.nsIFeedWriter, Ci.nsIClassInfo, Ci.nsISupports];
-    countRef.value = interfaces.length;
-    return interfaces;
-  },
-  getHelperForLanguage: function FW_getHelperForLanguage(language) null,
-  classID: Components.ID("{49bb6593-3aff-4eb3-a068-2712c28bd58e}"),
-  implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-  flags: Ci.nsIClassInfo.DOM_OBJECT,
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsIFeedWriter, Ci.nsIClassInfo,
+  classID: FEEDWRITER_CID,
+  classInfo: XPCOMUtils.generateCI({classID: FEEDWRITER_CID,
+                                    contractID: FEEDWRITER_CONTRACTID,
+                                    interfaces: [Ci.nsIFeedWriter],
+                                    flags: Ci.nsIClassInfo.DOM_OBJECT}),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIFeedWriter,
                                          Ci.nsIDOMEventListener, Ci.nsIObserver,
                                          Ci.nsINavHistoryObserver])
 };
diff --git a/browser/components/feeds/src/WebContentConverter.js b/browser/components/feeds/src/WebContentConverter.js
index 4e3c8f2d39a..78f61eb28d0 100644
--- a/browser/components/feeds/src/WebContentConverter.js
+++ b/browser/components/feeds/src/WebContentConverter.js
@@ -911,23 +911,14 @@ WebContentConverterRegistrar.prototype = {
     return this.QueryInterface(iid);
   },
 
-  /**
-   * See nsIClassInfo
-   */
-  getInterfaces: function WCCR_getInterfaces(countRef) {
-    var interfaces = 
-        [Ci.nsIWebContentConverterService, Ci.nsIWebContentHandlerRegistrar,
-         Ci.nsIObserver, Ci.nsIClassInfo, Ci.nsIFactory, Ci.nsISupports];
-    countRef.value = interfaces.length;
-    return interfaces;
-  },
-  getHelperForLanguage: function WCCR_getHelperForLanguage(language) {
-    return null;
-  },
   classID: WCCR_CLASSID,
-  implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-  flags: Ci.nsIClassInfo.DOM_OBJECT,
-  
+  classInfo: XPCOMUtils.generateCI({classID: WCCR_CLASSID,
+                                    contractID: WCCR_CONTRACTID,
+                                    interfaces: [Ci.nsIWebContentConverterService,
+                                                 Ci.nsIWebContentHandlerRegistrar,
+                                                 Ci.nsIObserver, Ci.nsIFactory],
+                                    flags: Ci.nsIClassInfo.DOM_OBJECT}),
+
   /**
    * See nsISupports
    */
@@ -935,9 +926,7 @@ WebContentConverterRegistrar.prototype = {
      [Ci.nsIWebContentConverterService, 
       Ci.nsIWebContentHandlerRegistrar,
       Ci.nsIObserver,
-      Ci.nsIClassInfo,
-      Ci.nsIFactory,
-      Ci.nsISupports]),
+      Ci.nsIFactory]),
 
   _xpcom_categories: [{
     category: "app-startup",
diff --git a/browser/components/sidebar/src/nsSidebar.js b/browser/components/sidebar/src/nsSidebar.js
index b2654cb73a3..4cd31b2ba21 100644
--- a/browser/components/sidebar/src/nsSidebar.js
+++ b/browser/components/sidebar/src/nsSidebar.js
@@ -46,8 +46,8 @@ Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 const DEBUG = false; /* set to false to suppress debug messages */
 
+const SIDEBAR_CONTRACTID        = "@mozilla.org/sidebar;1";
 const SIDEBAR_CID               = Components.ID("{22117140-9c6e-11d3-aaf1-00805f8a4905}");
-const nsISupports               = Components.interfaces.nsISupports;
 const nsISidebar                = Components.interfaces.nsISidebar;
 const nsISidebarExternal        = Components.interfaces.nsISidebarExternal;
 const nsIClassInfo              = Components.interfaces.nsIClassInfo;
@@ -214,32 +214,13 @@ function (aSearchURL)
   return 0;
 }
 
-// property of nsIClassInfo
-nsSidebar.prototype.flags = nsIClassInfo.DOM_OBJECT;
+nsSidebar.prototype.classInfo = XPCOMUtils.generateCI({classID: SIDEBAR_CID,
+                                                       contractID: SIDEBAR_CONTRACTID,
+                                                       classDescription: "Sidebar",
+                                                       interfaces: [nsISidebar, nsISidebarExternal],
+                                                       flags: nsIClassInfo.DOM_OBJECT});
 
-// property of nsIClassInfo
-nsSidebar.prototype.classDescription = "Sidebar";
-
-// method of nsIClassInfo
-nsSidebar.prototype.getInterfaces = function(count) {
-    var interfaceList = [nsISidebar, nsISidebarExternal, nsIClassInfo];
-    count.value = interfaceList.length;
-    return interfaceList;
-}
-
-// method of nsIClassInfo
-nsSidebar.prototype.getHelperForLanguage = function(count) {return null;}
-
-nsSidebar.prototype.QueryInterface =
-function (iid) {
-    if (iid.equals(nsISidebar) ||
-        iid.equals(nsISidebarExternal) ||
-        iid.equals(nsIClassInfo) ||
-        iid.equals(nsISupports))
-        return this;
-
-    throw Components.results.NS_ERROR_NO_INTERFACE;
-};
+nsSidebar.prototype.QueryInterface = XPCOMUtils.generateQI([nsISidebar, nsISidebarExternal]);
 
 var NSGetFactory = XPCOMUtils.generateNSGetFactory([nsSidebar]);
 
diff --git a/browser/fuel/src/fuelApplication.js b/browser/fuel/src/fuelApplication.js
index 6310af5501b..8d7ec94d24b 100644
--- a/browser/fuel/src/fuelApplication.js
+++ b/browser/fuel/src/fuelApplication.js
@@ -40,6 +40,9 @@ const Cc = Components.classes;
 
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 
+const APPLICATION_CID = Components.ID("fe74cf80-aa2d-11db-abbd-0800200c9a66");
+const APPLICATION_CONTRACTID = "@mozilla.org/fuel/application;1";
+
 //=================================================
 // Singleton that holds services and utilities
 var Utilities = {
@@ -668,21 +671,22 @@ function Application() {
 // Application implementation
 Application.prototype = {
   // for nsIClassInfo + XPCOMUtils
-  classID:          Components.ID("fe74cf80-aa2d-11db-abbd-0800200c9a66"),
+  classID:          APPLICATION_CID,
 
   // redefine the default factory for XPCOMUtils
   _xpcom_factory: ApplicationFactory,
 
   // for nsISupports
   QueryInterface : XPCOMUtils.generateQI([Ci.fuelIApplication, Ci.extIApplication,
-                                          Ci.nsIObserver, Ci.nsIClassInfo]),
+                                          Ci.nsIObserver]),
 
-  getInterfaces : function app_gi(aCount) {
-    var interfaces = [Ci.fuelIApplication, Ci.extIApplication, Ci.nsIObserver,
-                      Ci.nsIClassInfo];
-    aCount.value = interfaces.length;
-    return interfaces;
-  },
+  // for nsIClassInfo
+  classInfo: XPCOMUtils.generateCI({classID: APPLICATION_CID,
+                                    contractID: APPLICATION_CONTRACTID,
+                                    interfaces: [Ci.fuelIApplication,
+                                                 Ci.extIApplication,
+                                                 Ci.nsIObserver],
+                                    flags: Ci.nsIClassInfo.SINGLETON}),
 
   // for nsIObserver
   observe: function app_observe(aSubject, aTopic, aData) {
diff --git a/content/xslt/src/xslt/txEXSLTRegExFunctions.js b/content/xslt/src/xslt/txEXSLTRegExFunctions.js
index 4807cbc4ca9..e257d16df5a 100644
--- a/content/xslt/src/xslt/txEXSLTRegExFunctions.js
+++ b/content/xslt/src/xslt/txEXSLTRegExFunctions.js
@@ -40,8 +40,8 @@
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
 
 const EXSLT_REGEXP_CID = Components.ID("{18a03189-067b-4978-b4f1-bafe35292ed6}");
+const EXSLT_REGEXP_CONTRACTID = "@mozilla.org/exslt/regexp;1";
 
-const CATMAN_CONTRACTID = "@mozilla.org/categorymanager;1";
 const NODESET_CONTRACTID = "@mozilla.org/transformiix-nodeset;1";
 
 const Ci = Components.interfaces;
@@ -55,32 +55,11 @@ var SingletonInstance = null;
 txEXSLTRegExFunctions.prototype = {
     classID: EXSLT_REGEXP_CID,
 
-    QueryInterface: function(iid) {
-        if (iid.equals(Ci.nsISupports) ||
-            iid.equals(Ci.nsIClassInfo) ||
-            iid.equals(Ci.txIEXSLTRegExFunctions))
-            return this;
-
-        throw Components.results.NS_ERROR_NO_INTERFACE;
-    },
-
-    // nsIClassInfo
-    getInterfaces: function(countRef) {
-        var interfaces = [
-            Ci.txIEXSLTRegExFunctions
-        ];
-        countRef.value = interfaces.length;
-
-        return interfaces;
-    },
-
-    getHelperForLanguage: function(language) {
-        return null;
-    },
-
-    implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-    flags: 0,
+    QueryInterface: XPCOMUtils.generateQI([Ci.txIEXSLTRegExFunctions]),
 
+    classInfo: XPCOMUtils.generateCI({classID: EXSLT_REGEXP_CID,
+                                      contractID: EXSLT_REGEXP_CONTRACTID,
+                                      interfaces: [Ci.txIEXSLTRegExFunctions]}),
 
     // txIEXSLTRegExFunctions
     match: function(context, str, regex, flags) {
diff --git a/dom/system/GPSDGeolocationProvider.js b/dom/system/GPSDGeolocationProvider.js
index a0e1469e2c5..f2f9bd0ecb6 100644
--- a/dom/system/GPSDGeolocationProvider.js
+++ b/dom/system/GPSDGeolocationProvider.js
@@ -68,21 +68,12 @@ function GeoPositionCoordsObject(latitude, longitude, altitude, accuracy, altitu
 
 GeoPositionCoordsObject.prototype = {
 
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDOMGeoPositionCoords, Ci.nsIClassInfo]),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDOMGeoPositionCoords]),
   
   // Class Info is required to be able to pass objects back into the DOM.
-  getInterfaces: function(countRef) {
-    var interfaces = [Ci.nsIDOMGeoPositionCoords, Ci.nsIClassInfo, Ci.nsISupports];
-    countRef.value = interfaces.length;
-    return interfaces;
-  },
-  
-  getHelperForLanguage: function(language) null,
-  contractID: null,
-  classDescription: "Geoposition Coordinate Object",
-  classID: null,
-  implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-  flags: Ci.nsIClassInfo.DOM_OBJECT,
+  classInfo: XPCOMUtils.generateCI({interfaces: [Ci.nsIDOMGeoPositionCoords],
+                                    flags: Ci.nsIClassInfo.DOM_OBJECT,
+                                    classDescription: "Geoposition Coordinate Object"}),
 
   latitude: null,
   longitude: null,
@@ -101,21 +92,12 @@ function GeoPositionObject(latitude, longitude, altitude, accuracy, altitudeAccu
 
 GeoPositionObject.prototype = {
 
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDOMGeoPosition, Ci.nsIClassInfo]),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDOMGeoPosition]),
 
   // Class Info is required to be able to pass objects back into the DOM.
-  getInterfaces: function(countRef) {
-    var interfaces = [Ci.nsIDOMGeoPosition, Ci.nsIClassInfo, Ci.nsISupports];
-    countRef.value = interfaces.length;
-    return interfaces;
-  },
-
-  getHelperForLanguage: function(language) null,
-  contractID: null,
-  classDescription: "Geoposition Object",
-  classID: null,
-  implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-  flags: Ci.nsIClassInfo.DOM_OBJECT,
+  classInfo: XPCOMUtils.generateCI({interfaces: [Ci.nsIDOMGeoPosition],
+                                    flags: Ci.nsIClassInfo.DOM_OBJECT,
+                                    classDescription: "Geoposition Object"}),
 
   coords: null,
   timestamp: null,
diff --git a/dom/system/NetworkGeolocationProvider.js b/dom/system/NetworkGeolocationProvider.js
index fe48420f4b4..8762d8ca70c 100755
--- a/dom/system/NetworkGeolocationProvider.js
+++ b/dom/system/NetworkGeolocationProvider.js
@@ -35,17 +35,10 @@ function WifiGeoAddressObject(streetNumber, street, premises, city, county, regi
 
 WifiGeoAddressObject.prototype = {
 
-    QueryInterface:   XPCOMUtils.generateQI([Ci.nsIDOMGeoPositionAddress, Ci.nsIClassInfo]),
+    QueryInterface:   XPCOMUtils.generateQI([Ci.nsIDOMGeoPositionAddress]),
 
-    getInterfaces: function(countRef) {
-        var interfaces = [Ci.nsIDOMGeoPositionAddress, Ci.nsIClassInfo, Ci.nsISupports];
-        countRef.value = interfaces.length;
-        return interfaces;
-    },
-
-    getHelperForLanguage: function(language) null,
-    implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-    flags: Ci.nsIClassInfo.DOM_OBJECT,
+    classInfo: XPCOMUtils.generateCI({interfaces: [Ci.nsIDOMGeoPositionAddress],
+                                      flags: Ci.nsIClassInfo.DOM_OBJECT})
 };
 
 function WifiGeoCoordsObject(lat, lon, acc, alt, altacc) {
@@ -58,18 +51,11 @@ function WifiGeoCoordsObject(lat, lon, acc, alt, altacc) {
 
 WifiGeoCoordsObject.prototype = {
 
-    QueryInterface:   XPCOMUtils.generateQI([Ci.nsIDOMGeoPositionCoords, Ci.nsIClassInfo]),
+    QueryInterface:   XPCOMUtils.generateQI([Ci.nsIDOMGeoPositionCoords]),
 
-    getInterfaces: function(countRef) {
-        var interfaces = [Ci.nsIDOMGeoPositionCoords, Ci.nsIClassInfo, Ci.nsISupports];
-        countRef.value = interfaces.length;
-        return interfaces;
-    },
-
-    getHelperForLanguage: function(language) null,
-    classDescription: "wifi geo position coords object",
-    implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-    flags: Ci.nsIClassInfo.DOM_OBJECT,
+    classInfo: XPCOMUtils.generateCI({interfaces: [Ci.nsIDOMGeoPositionCoords],
+                                      flags: Ci.nsIClassInfo.DOM_OBJECT,
+                                      classDescription: "wifi geo position coords object"}),
 
     latitude: 0,
     longitude: 0,
@@ -107,19 +93,12 @@ function WifiGeoPositionObject(location) {
 
 WifiGeoPositionObject.prototype = {
 
-    QueryInterface:   XPCOMUtils.generateQI([Ci.nsIDOMGeoPosition, Ci.nsIClassInfo]),
+    QueryInterface:   XPCOMUtils.generateQI([Ci.nsIDOMGeoPosition]),
 
     // Class Info is required to be able to pass objects back into the DOM.
-    getInterfaces: function(countRef) {
-        var interfaces = [Ci.nsIDOMGeoPosition, Ci.nsIClassInfo, Ci.nsISupports];
-        countRef.value = interfaces.length;
-        return interfaces;
-    },
-
-    getHelperForLanguage: function(language) null,
-    classDescription: "wifi geo location position object",
-    implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-    flags: Ci.nsIClassInfo.DOM_OBJECT,
+    classInfo: XPCOMUtils.generateCI({interfaces: [Ci.nsIDOMGeoPosition],
+                                      flags: Ci.nsIClassInfo.DOM_OBJECT,
+                                      classDescription: "wifi geo location position object"}),
 
     coords: null,
     timestamp: 0,
diff --git a/js/src/xpconnect/loader/XPCOMUtils.jsm b/js/src/xpconnect/loader/XPCOMUtils.jsm
index 42787ef847b..0b4d2e51fe8 100644
--- a/js/src/xpconnect/loader/XPCOMUtils.jsm
+++ b/js/src/xpconnect/loader/XPCOMUtils.jsm
@@ -68,6 +68,19 @@
  *       "nsIFoo",
  *       "nsIBar" ]),
  *
+ *    // [optional] classInfo implementation, e.g. using the generateCI helper.
+ *    // Will be automatically returned from QueryInterface if that was
+ *    // generated with the generateQI helper.
+ *    classInfo: XPCOMUtils.generateCI(
+ *      {classID: Components.ID("{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}"),
+ *       contractID: "@example.com/xxx;1",
+ *       classDescription: "unique text description",
+ *       interfaces: [Components.interfaces.nsIObserver,
+ *                    Components.interfaces.nsIMyInterface,
+ *                    "nsIFoo",
+ *                    "nsIBar"],
+ *       flags: Ci.nsIClassInfo.SINGLETON}),
+ *
  *    // The following properties were used prior to Mozilla 2, but are no
  *    // longer supported. They may still be included for compatibility with
  *    // prior versions of XPCOMUtils. In Mozilla 2, this information is
@@ -122,12 +135,44 @@ var XPCOMUtils = {
    * assigned to the 'QueryInterface' property of a JS object. When invoked on
    * that object, it checks if the given iid is listed in the |interfaces|
    * param, and if it is, returns |this| (the object it was called on).
+   * If the JS object has a classInfo property it'll be returned for the
+   * nsIClassInfo IID, generateCI can be used to generate the classInfo
+   * property.
    */
   generateQI: function XPCU_generateQI(interfaces) {
     /* Note that Ci[Ci.x] == Ci.x for all x */
     return makeQI([Ci[i].name for each (i in interfaces) if (Ci[i])]);
   },
 
+  /**
+   * Generate a ClassInfo implementation for a component. The returned object
+   * must be assigned to the 'classInfo' property of a JS object. The first and
+   * only argument should be an object that contains a number of optional
+   * properties: "interfaces", "contractID", "classDescription", "classID" and
+   * "flags". The values of the properties will be returned as the values of the
+   * various properties of the nsIClassInfo implementation.
+   */
+  generateCI: function XPCU_generateCI(classInfo)
+  {
+    if (QueryInterface in classInfo)
+      throw Error("In generateCI, don't use a component for generating classInfo");
+    /* Note that Ci[Ci.x] == Ci.x for all x */
+    var _interfaces = [Ci[i] for each (i in classInfo.interfaces) if (Ci[i])];
+    return {
+      getInterfaces: function XPCU_getInterfaces(countRef) {
+        countRef.value = _interfaces.length;
+        return _interfaces;
+      },
+      getHelperForLanguage: function XPCU_getHelperForLanguage(language) null,
+      contractID: classInfo.contractID,
+      classDescription: classInfo.classDescription,
+      classID: classInfo.classID,
+      implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
+      flags: classInfo.flags,
+      QueryInterface: this.generateQI([Ci.nsIClassInfo])
+    };
+  },
+
   /**
    * Generate a NSGetFactory function given an array of components.
    */
@@ -281,6 +326,8 @@ function makeQI(interfaceNames) {
   return function XPCOMUtils_QueryInterface(iid) {
     if (iid.equals(Ci.nsISupports))
       return this;
+    if (iid.equals(Ci.nsIClassInfo) && "classInfo" in this)
+      return this.classInfo;
     for each(let interfaceName in interfaceNames) {
       if (Ci[interfaceName].equals(iid))
         return this;
diff --git a/js/src/xpconnect/tests/unit/test_xpcomutils.js b/js/src/xpconnect/tests/unit/test_xpcomutils.js
index 7d337bb4a9b..c9ab5b2e767 100644
--- a/js/src/xpconnect/tests/unit/test_xpcomutils.js
+++ b/js/src/xpconnect/tests/unit/test_xpcomutils.js
@@ -76,6 +76,31 @@ function test_generateQI_string_names()
 }
 
 
+function test_generateCI()
+{
+    const classID = Components.ID("562dae2e-7cff-432b-995b-3d4c03fa2b89");
+    const classDescription = "generateCI test component";
+    const flags = Components.interfaces.nsIClassInfo.DOM_OBJECT;
+    var x = {
+        QueryInterface: XPCOMUtils.generateQI([]),
+        classInfo: XPCOMUtils.generateCI({classID: classID,
+                                          interfaces: [],
+                                          flags: flags,
+                                          classDescription: classDescription})
+    };
+
+    try {
+        var ci = x.QueryInterface(Components.interfaces.nsIClassInfo);
+        ci = ci.QueryInterface(Components.interfaces.nsISupports);
+        ci = ci.QueryInterface(Components.interfaces.nsIClassInfo);
+        do_check_eq(ci.classID, classID);
+        do_check_eq(ci.flags, flags);
+        do_check_eq(ci.classDescription, classDescription);
+    } catch(e) {
+        do_throw("Classinfo for x should not be missing or broken");
+    }
+}
+
 function test_defineLazyGetter()
 {
     let accessCount = 0;
@@ -186,6 +211,7 @@ function test_categoryRegistration()
 
 let tests = [
     test_generateQI_string_names,
+    test_generateCI,
     test_defineLazyGetter,
     test_defineLazyServiceGetter,
     test_categoryRegistration,
diff --git a/mobile/components/Sidebar.js b/mobile/components/Sidebar.js
index dadfb374a37..7aa66741b82 100644
--- a/mobile/components/Sidebar.js
+++ b/mobile/components/Sidebar.js
@@ -48,6 +48,9 @@ const Cu = Components.utils;
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 
+const SIDEBAR_CID = Components.ID("{22117140-9c6e-11d3-aaf1-00805f8a4905}");
+const SIDEBAR_CONTRACTID = "@mozilla.org/sidebar;1";
+
 function Sidebar() {
   // Depending on if we are in the parent or child, prepare to remote
   // certain calls
@@ -167,24 +170,19 @@ Sidebar.prototype = {
   },
 
   // =========================== nsIClassInfo ===========================
-  flags: Ci.nsIClassInfo.DOM_OBJECT,
-  classDescription: "Sidebar",
-  getInterfaces: function getInterfaces(count) {
-    var interfaceList = [Ci.nsISidebar, Ci.nsISidebarExternal, Ci.nsIClassInfo];
-    count.value = interfaceList.length;
-    return interfaceList;
-  },
-  getHelperForLanguage: function getHelperForLanguage(count) {
-    return null;
-  },
+  classInfo: XPCOMUtils.generateCI({classID: SIDEBAR_CID,
+                                    contractID: SIDEBAR_CONTRACTID,
+                                    interfaces: [Ci.nsISidebar,
+                                                 Ci.nsISidebarExternal],
+                                    flags: Ci.nsIClassInfo.DOM_OBJECT,
+                                    classDescription: "Sidebar"}),
 
   // =========================== nsISupports ===========================
   QueryInterface: XPCOMUtils.generateQI([Ci.nsISidebar,
-                                         Ci.nsISidebarExternal,
-                                         Ci.nsIClassInfo]),
+                                         Ci.nsISidebarExternal]),
 
   // XPCOMUtils stuff
-  classID: Components.ID("{22117140-9c6e-11d3-aaf1-00805f8a4905}"),
+  classID: SIDEBAR_CID,
 };
 
 const NSGetFactory = XPCOMUtils.generateNSGetFactory([Sidebar]);
diff --git a/toolkit/components/exthelper/extApplication.js b/toolkit/components/exthelper/extApplication.js
index d1a96e39f1a..f5d026c74b1 100644
--- a/toolkit/components/exthelper/extApplication.js
+++ b/toolkit/components/exthelper/extApplication.js
@@ -556,19 +556,9 @@ extApplication.prototype = {
     this._registered = {"unload": true};
   },
 
-  // for nsIClassInfo
-  flags : Ci.nsIClassInfo.SINGLETON,
-  implementationLanguage : Ci.nsIProgrammingLanguage.JAVASCRIPT,
-
-  getInterfaces : function app_gi(aCount) {
-    var interfaces = [Ci.extIApplication, Ci.nsIObserver, Ci.nsIClassInfo];
-    aCount.value = interfaces.length;
-    return interfaces;
-  },
-
-  getHelperForLanguage : function app_ghfl(aCount) {
-    return null;
-  },
+  classInfo: XPCOMUtils.generateCI({interfaces: [Ci.extIApplication,
+                                                 Ci.nsIObserver],
+                                    flags: Ci.nsIClassInfo.SINGLETON}),
 
   // extIApplication
   get id() {
diff --git a/toolkit/mozapps/update/nsUpdateService.js b/toolkit/mozapps/update/nsUpdateService.js
index 9a0845295c1..3a5c3d7431b 100644
--- a/toolkit/mozapps/update/nsUpdateService.js
+++ b/toolkit/mozapps/update/nsUpdateService.js
@@ -51,6 +51,9 @@ const Cc = Components.classes;
 const Ci = Components.interfaces;
 const Cr = Components.results;
 
+const UPDATESERVICE_CID = Components.ID("{B3C290A6-3943-4B89-8BBE-C01EB7B3B311}");
+const UPDATESERVICE_CONTRACTID = "@mozilla.org/updates/update-service;1";
+
 const PREF_APP_UPDATE_ALTWINDOWTYPE       = "app.update.altwindowtype";
 const PREF_APP_UPDATE_AUTO                = "app.update.auto";
 const PREF_APP_UPDATE_BACKGROUND_INTERVAL = "app.update.download.backgroundInterval";
@@ -1778,19 +1781,14 @@ UpdateService.prototype = {
     return this._downloader && this._downloader.isBusy;
   },
 
-  // nsIClassInfo
-  flags: Ci.nsIClassInfo.SINGLETON,
-  implementationLanguage: Ci.nsIProgrammingLanguage.JAVASCRIPT,
-  getHelperForLanguage: function(language) null,
-  getInterfaces: function AUS_getInterfaces(count) {
-    var interfaces = [Ci.nsIApplicationUpdateService,
-                      Ci.nsITimerCallback,
-                      Ci.nsIObserver];
-    count.value = interfaces.length;
-    return interfaces;
-  },
+  classID: UPDATESERVICE_CID,
+  classInfo: XPCOMUtils.generateCI({classID: UPDATESERVICE_CID,
+                                    contractID: UPDATESERVICE_CONTRACTID,
+                                    interfaces: [Ci.nsIApplicationUpdateService,
+                                                 Ci.nsITimerCallback,
+                                                 Ci.nsIObserver],
+                                    flags: Ci.nsIClassInfo.SINGLETON}),
 
-  classID: Components.ID("{B3C290A6-3943-4B89-8BBE-C01EB7B3B311}"),
   _xpcom_factory: UpdateServiceFactory,
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIApplicationUpdateService,
                                          Ci.nsIAddonUpdateCheckListener,