--- a/js/xpconnect/loader/XPCOMUtils.jsm
+++ b/js/xpconnect/loader/XPCOMUtils.jsm
@@ -336,46 +336,50 @@ this.XPCOMUtils = {
       Services.prefs.addObserver(aPreference, observer, true);
 
       defineGetter(lazyGetter);
       return lazyGetter();
     });
   },
 
   /**
-   * Convenience access to category manager
-   */
-  get categoryManager() {
-    return Components.classes["@mozilla.org/categorymanager;1"]
-           .getService(Ci.nsICategoryManager);
-  },
-
-  /**
    * Helper which iterates over a nsISimpleEnumerator.
    * @param e The nsISimpleEnumerator to iterate over.
    * @param i The expected interface for each element.
    */
-  IterSimpleEnumerator: function XPCU_IterSimpleEnumerator(e, i)
+  IterSimpleEnumerator: function* XPCU_IterSimpleEnumerator(e, i)
   {
     while (e.hasMoreElements())
       yield e.getNext().QueryInterface(i);
   },
 
   /**
    * Helper which iterates over a string enumerator.
    * @param e The string enumerator (nsIUTF8StringEnumerator or
    *          nsIStringEnumerator) over which to iterate.
    */
-  IterStringEnumerator: function XPCU_IterStringEnumerator(e)
+  IterStringEnumerator: function* XPCU_IterStringEnumerator(e)
   {
     while (e.hasMore())
       yield e.getNext();
   },
 
   /**
+   * Helper which iterates over the entries in a category.
+   * @param aCategory The name of the category over which to iterate.
+   */
+  enumerateCategoryEntries: function* XPCOMUtils_enumerateCategoryEntries(aCategory)
+  {
+    let category = this.categoryManager.enumerateCategory(aCategory);
+    for (let entry of this.IterSimpleEnumerator(category, Ci.nsISupportsCString)) {
+      yield [entry.data, this.categoryManager.getCategoryEntry(aCategory, entry.data)];
+    }
+  },
+
+  /**
    * Returns an nsIFactory for |component|.
    */
   _getFactory: function XPCOMUtils__getFactory(component) {
     var factory = component.prototype._xpcom_factory;
     if (!factory) {
       factory = {
         createInstance: function(outer, iid) {
           if (outer)
@@ -439,16 +443,20 @@ this.XPCOMUtils = {
   },
 };
 
 XPCOMUtils.defineLazyModuleGetter(this, "Preferences",
                                   "resource://gre/modules/Preferences.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Services",
                                   "resource://gre/modules/Services.jsm");
 
+XPCOMUtils.defineLazyServiceGetter(XPCOMUtils, "categoryManager",
+                                   "@mozilla.org/categorymanager;1",
+                                   "nsICategoryManager");
+
 /**
  * Helper for XPCOMUtils.generateQI to avoid leaks - see bug 381651#c1
  */
 function makeQI(interfaceNames) {
   return function XPCOMUtils_QueryInterface(iid) {
     if (iid.equals(Ci.nsISupports))
       return this;
     if (iid.equals(Ci.nsIClassInfo) && "classInfo" in this)

--- a/js/xpconnect/tests/unit/test_xpcomutils.js
+++ b/js/xpconnect/tests/unit/test_xpcomutils.js
@@ -183,32 +183,30 @@ add_test(function test_categoryRegistrat
     "XULAppInfo",
     XULAPPINFO_CONTRACTID,
     XULAppInfoFactory
   );
 
   // Load test components.
   do_load_manifest("CatRegistrationComponents.manifest");
 
-  const EXPECTED_ENTRIES = ["CatAppRegisteredComponent",
-                            "CatRegisteredComponent"];
+  const EXPECTED_ENTRIES = new Map([
+    ["CatRegisteredComponent", "@unit.test.com/cat-registered-component;1"],
+    ["CatAppRegisteredComponent", "@unit.test.com/cat-app-registered-component;1"],
+  ]);
 
-  // Check who is registered in "test-cat" category.
-  let foundEntriesCount = 0;
-  let catMan = Cc["@mozilla.org/categorymanager;1"].
-               getService(Ci.nsICategoryManager);
-  let entries = catMan.enumerateCategory(CATEGORY_NAME);
-  while (entries.hasMoreElements()) {
-    foundEntriesCount++;
-    let entry = entries.getNext().QueryInterface(Ci.nsISupportsCString).data;
-    print("Check the found category entry (" + entry + ") is expected.");  
-    do_check_true(EXPECTED_ENTRIES.indexOf(entry) != -1);
+  // Verify the correct entries are registered in the "test-cat" category.
+  for (let [name, value] of XPCOMUtils.enumerateCategoryEntries(CATEGORY_NAME)) {
+    print("Verify that the name/value pair exists in the expected entries.");
+    ok(EXPECTED_ENTRIES.has(name));
+    do_check_eq(EXPECTED_ENTRIES.get(name), value);
+    EXPECTED_ENTRIES.delete(name);
   }
-  print("Check there are no more or less than expected entries.");
-  do_check_eq(foundEntriesCount, EXPECTED_ENTRIES.length);
+  print("Check that all of the expected entries have been deleted.");
+  do_check_eq(EXPECTED_ENTRIES.size, 0);
   run_next_test();
 });
 
 add_test(function test_generateSingletonFactory()
 {
   const XPCCOMPONENT_CONTRACTID = "@mozilla.org/singletonComponentTest;1";
   const XPCCOMPONENT_CID = Components.ID("{31031c36-5e29-4dd9-9045-333a5d719a3e}");
 

--- a/xpcom/ds/nsINIProcessor.js
+++ b/xpcom/ds/nsINIProcessor.js
@@ -70,19 +70,19 @@ INIProcessor.prototype = {
      */
     _readFile : function() {
         // If file doesn't exist, there's nothing to do.
         if (!this._iniFile.exists() || 0 == this._iniFile.fileSize)
             return;
 
         let iniParser = Cc["@mozilla.org/xpcom/ini-parser-factory;1"]
             .getService(Ci.nsIINIParserFactory).createINIParser(this._iniFile);
-        for (let section in XPCOMUtils.IterStringEnumerator(iniParser.getSections())) {
+        for (let section of XPCOMUtils.IterStringEnumerator(iniParser.getSections())) {
             this._iniData[section] = {};
-            for (let key in XPCOMUtils.IterStringEnumerator(iniParser.getKeys(section))) {
+            for (let key of XPCOMUtils.IterStringEnumerator(iniParser.getKeys(section))) {
                 this._iniData[section][key] = iniParser.getString(section, key);
             }
         }
     },
 
     // nsIINIParser
 
     getSections : function() {