In keeping with Adobe's convention, Set and Map's forEach() function takes an optional 'thisObject' param

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5502 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/HashSet.as

@@ -76,10 +76,10 @@ public class HashSet
         return (_hashMap.containsKey(o));
     }
 
-    public function forEach (fn :Function) :void
+    public function forEach (fn :Function, thisObject :* = null) :void
     {
         _hashMap.forEach(function (key :Object, val :Object) :void {
-            fn(key);
+            fn.call(thisObject, key);
         });
     }