ES6: Update unscopables to match spec

test/mjsunit/harmony/proxies-with-unscopables.js

 // Copyright 2014 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: --harmony-proxies
 
 
 // TODO(arv): Once proxies can intercept symbols, add more tests.
 
 
@@ skipping 56 matching lines @@
 
 
 function TestUseProxyAsUnscopables() {
   var x = 1;
   var object = {
     x: 2
   };
   var calls = 0;
   var proxy = Proxy.create({
     has: function(key) {
+      assertUnreachable();
+    },
+    getPropertyDescriptor: function(key) {
       calls++;
       assertEquals('x', key);
-      return calls === 2;
-    },
-    getPropertyDescriptor: function(key) {
-      assertUnreachable();
+      return {
+        value: calls === 2 ? true : undefined,
+        configurable: true,
+        enumerable: true,
+        writable: true,
+      };
     }
   });
 
   object[Symbol.unscopables] = proxy;
 
   with (object) {
     assertEquals(2, x);
     assertEquals(1, x);
   }
 
   // HasBinding, HasBinding
   assertEquals(2, calls);
 }
 TestUseProxyAsUnscopables();
 
 
 function TestThrowInHasUnscopables() {
   var x = 1;
   var object = {
     x: 2
   };
 
   function CustomError() {}
 
   var calls = 0;
   var proxy = Proxy.create({
     has: function(key) {
+      assertUnreachable();
+    },
+    getPropertyDescriptor: function(key) {
       if (calls++ === 0) {
         throw new CustomError();
       }
       assertUnreachable();
-    },
-    getPropertyDescriptor: function(key) {
-      assertUnreachable();
     }
   });
 
   object[Symbol.unscopables] = proxy;
 
   assertThrows(function() {
     with (object) {
       x;
     }
   }, CustomError);
@@ skipping 16 matching lines @@
 
   global.x = 2;
   assertEquals(2, global.x);
   assertEquals(2, x);
 
   x = 3;
   assertEquals(3, global.x);
   assertEquals(3, x);
 }
 TestGlobalShouldIgnoreUnscopables();