Only walk the hidden prototype chain for private nonexistent symbols

test/mjsunit/regress/regress-479528.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --allow-natives-syntax
 
-function foo(x) {
-  if (x === undefined) return;
-  while (true) {
-    while (1 || 2) { }
-    f();
-  }
+var __v_7 = {"__proto__": this};
+__v_9 = %CreatePrivateSymbol("__v_9");
+this[__v_9] = "moo";
+function __f_5() {
+    __v_7[__v_9] = "bow-wow";
 }
-%OptimizeFunctionOnNextCall(foo);
-foo();
+__f_5();