[wasm] Freeze exports object

test/mjsunit/wasm/add-getters.js

 // Copyright 2016 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: --expose-wasm
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
 function testAddGetter(object, name, val) {
   Object.defineProperty(object, name, { get: function() { return val; } });
   assertSame(val, object[name]);
 }
 
+function testAddGetterFails(object, name, val) {
+  function assign() {
+    Object.defineProperty(object, name, { get: function() { return val; } });
+  }
+  assertThrows(assign, TypeError);
+}
+
 function testAddGetterBothWays(object, name, val) {
   print("Object.defineProperty");
   Object.defineProperty(object, name, { get: function() { return val; } });
   print("object.__defineGetter__");
   object.__defineGetter__(name, () => val);
   assertSame(val, object[name]);
 }
 
 function testFailToAddGetter(object, name, val) {
   assertThrows(() => Object.defineProperty(object, name, { get: function() { return val; } }));
@@ skipping 32 matching lines @@
   var instance = builder.instantiate();
   testAddGetter(instance, "exports", 290);
   testAddGetter(instance, "xyz", new Object());
 })();
 
 (function TestAddGetterToExports() {
   print("TestAddGetterToExports...");
   var builder = makeBuilder();
   var exports = builder.instantiate().exports;
   testFailToAddGetter(exports, "f", 9834);
-  testAddGetter(exports, "nag", new Number(2));
+  testAddGetterFails(exports, "nag", new Number(2));
 })();