Major and winning overhaul to for-in codegen (mad props to Andreas for advice).

js/src/jsbuiltins.cpp

@@ -367,13 +367,22 @@ js_Any_setelem(JSContext* cx, JSObject* obj, JSString* idstr, jsval v)
 }
 
 JSObject* FASTCALL
-js_ValueToEnumerator(JSContext* cx, jsval v)
+js_FastValueToIterator(JSContext* cx, jsuint flags, jsval v)
 {
-    if (!js_ValueToIterator(cx, JSITER_ENUMERATE, &v))
+    if (!js_ValueToIterator(cx, flags, &v))
         return NULL;
     return JSVAL_TO_OBJECT(v);
 }
 
+jsval FASTCALL
+js_FastCallIteratorNext(JSContext* cx, JSObject* iterobj)
+{
+    jsval v;
+    if (!js_CallIteratorNext(cx, iterobj, &v))
+        return JSVAL_ERROR_COOKIE;
+    return v;
+}
+
 GuardRecord* FASTCALL
 js_CallTree(InterpState* state, Fragment* f)
 {