diff --git a/webapprt/WebappRTDirectoryProvider.js b/webapprt/WebappRTDirectoryProvider.js
index c4ae8ac6867..08f857ab7b1 100644
--- a/webapprt/WebappRTDirectoryProvider.js
+++ b/webapprt/WebappRTDirectoryProvider.js
@@ -7,7 +7,9 @@ const Ci = Components.interfaces;
 const Cu = Components.utils;
 
 const WEBAPP_REGISTRY_DIR = "WebappRegD";
+const NS_APP_CHROME_DIR_LIST = "AChromDL";
 
+Cu.import("resource://gre/modules/FileUtils.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/WebappRT.jsm");
 
@@ -16,7 +18,8 @@ function DirectoryProvider() {}
 DirectoryProvider.prototype = {
   classID: Components.ID("{e1799fda-4b2f-4457-b671-e0641d95698d}"),
 
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDirectoryServiceProvider]),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDirectoryServiceProvider,
+                                         Ci.nsIDirectoryServiceProvider2]),
 
   getFile: function(prop, persistent) {
     if (prop == WEBAPP_REGISTRY_DIR) {
@@ -28,7 +31,25 @@ DirectoryProvider.prototype = {
     // We return null to show failure instead of throwing an error,
     // which works with the way the interface is called (per bug 529077).
     return null;
-  }
+  },
+
+  getFiles: function(prop, persistent) {
+    if (prop == NS_APP_CHROME_DIR_LIST) {
+      return {
+        _done: false,
+        QueryInterface: XPCOMUtils.generateQI([Ci.nsISimpleEnumerator]),
+        hasMoreElements: function() {
+          return !this._done;
+        },
+        getNext: function() {
+          this._done = true;
+          return FileUtils.getDir("AppRegD", ["chrome"], false);
+        }
+      };
+    }
+
+    return null;
+  },
 };
 
 const NSGetFactory = XPCOMUtils.generateNSGetFactory([DirectoryProvider]);