[wasm] Freeze exports object

test/mjsunit/wasm/instantiate-module-basic.js

Index: test/mjsunit/wasm/instantiate-module-basic.js
diff --git a/test/mjsunit/wasm/instantiate-module-basic.js b/test/mjsunit/wasm/instantiate-module-basic.js
index 493bf7acd8da81ba2d9217e88092c142048f6b3d..d3a70dcda85d24a3a617bddffc8ae4222147a66f 100644
--- a/test/mjsunit/wasm/instantiate-module-basic.js
+++ b/test/mjsunit/wasm/instantiate-module-basic.js
@@ -25,6 +25,10 @@ function CheckInstance(instance) {
   assertFalse(instance === 0);
   assertEquals("object", typeof instance);
 
+  // Check the exports object is frozen.
+  assertFalse(Object.isExtensible(instance.exports));
+  assertTrue(Object.isFrozen(instance.exports));
+
   // Check the memory is an ArrayBuffer.
   var mem = instance.exports.memory;
   assertFalse(mem === undefined);