Allow global prototype to be a Proxy

test/mjsunit/es6/global-proto-proxy.js

+// Copyright 2017 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.
+
+var global = this;
+;(function () {
+  var calledDelete = false;
+  var calledGet = false;
+  var calledHas = false;
+  var calledSet = false;
+  var target = {};
+  var assertEquals = global.assertEquals;
+  var proxy = new Proxy(target, {
+    has(target, property) {
+      calledHas = true;
+      return Reflect.has(target, property);
+    },
+    get(target, property, receiver) {
+      calledGet = true;
+      return Reflect.get(target, property, receiver);
+    },
+    set(targer, property, value, receiver) {
+      calledSet = true;
+      return Reflect.set(target, property, value, receiver);
+    },
+    delete(target, property, receiver) {
+      calledDelete = true;
+      return Reflect.delete(target, property, receiver);
+    }
+  });
+  Object.setPrototypeOf(global, proxy);
+  getGlobal;
+  assertTrue(calledGet);
+  makeGlobal = 2;
+  assertTrue(calledSet);
+  "findGlobal" in global;
+  assertTrue(calledHas);
+  var deletedOwn = delete makeGlobal;
+  assertTrue(deletedOwn);
+  assertEquals(void 0, makeGlobal);
+})();