Fix arg maps.

common/modules/base.jsm

@@ -488,6 +488,14 @@ function call(fn) {
  * value of the property.
  */
 function memoize(obj, key, getter) {
+    if (arguments.length == 1) {
+        for (let prop in Object.getOwnPropertyNames(obj)) {
+            let get = objproto.__lookupGetter__.call(obj, prop);
+            if (get)
+                memoize(obj, prop, get);
+        }
+        return obj;
+    }
     obj.__defineGetter__(key, function g_replaceProperty() (
         Class.replaceProperty(this.instance || this, key, null),
         Class.replaceProperty(this.instance || this, key, getter.call(this, key))));

common/modules/util.jsm

@@ -761,7 +761,7 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
     isDomainURL: function isDomainURL(url, domain) util.isSubdomain(util.getHost(url), domain),
 
     /** Dactyl's notion of the current operating system platform. */
-    OS: {
+    OS: memoize({
         _arch: services.runtime.OS,
         /**
          * @property {string} The normalised name of the OS. This is one of
@@ -776,7 +776,7 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
         get isUnix() !this.isWindows && !this.isMacOSX,
         /** @property {RegExp} A RegExp which matches illegal characters in path components. */
         get illegalCharacters() this.isWindows ? /[<>:"/\\|?*\x00-\x1f]/ : /\//
-    },
+    }),
 
     /**
      * Returns true if *host* is a subdomain of *domain*.