Use evalInSandbox for :js rather than the subscript loader so that we can preserve file names/line numbers.

common/modules/base.jsm

@@ -66,7 +66,7 @@ if (!Object.getOwnPropertyDescriptor)
         return desc;
     };
 if (!Object.getOwnPropertyNames)
-    Object.getOwnPropertyNames = function getOwnPropertyNames(obj) {
+    Object.getOwnPropertyNames = function getOwnPropertyNames(obj, _debugger) {
         // This is an ugly and unfortunately necessary hack.
         if (hasOwnProperty.call(obj, "__iterator__")) {
             var oldIter = obj.__iterator__;

common/modules/services.jsm

@@ -124,7 +124,7 @@ const Services = Module("Services", {
 }, {
 }, {
     init: function (dactyl, modules) {
-        if (!this.get("extensionManager"))
+        if (!modules.AddonManager && !this.get("extensionManager"))
             Components.utils.import("resource://gre/modules/AddonManager.jsm", modules);
     },
     javascript: function (dactyl, modules) {