[wasm][asm.js] Make asm.js->wasm return a regular object.

test/mjsunit/asm/asm-validation.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: --validate-asm --allow-natives-syntax
 
 // Note that this test file contains tests that explicitly check modules are
 // valid asm.js and then break them with invalid instantiation arguments. If
 // this script is run more than once (e.g. --stress-opt) then modules remain
 // broken in the second run and assertions would fail. We prevent re-runs.
@@ skipping 458 matching lines @@
       b = b | 0;
       // Disallowed because conditional yields int, even when both sides
       // are signed.
       return 1 ? a | 0 : b | 0;
     }
     return foo;
   }
   Module();
   assertFalse(% IsAsmWasmCode(Module));
 })();
+
+(function TestAsmIsRegular() {
+  function Module() {
+    'use asm';
+    var g = 123;
+    function foo() {
+      return g | 0;
+    }
+    return {x: foo};
+  }
+  var o = Module();
+  assertValidAsm(Module);
+  assertFalse(o instanceof WebAssembly.Instance);
+  assertTrue(o instanceof Object);
+  assertTrue(o.__proto__ === Object.prototype);
+  o.x = 5;
+  assertTrue(typeof o.x === 'number');
+  assertTrue(o.__single_function__ === undefined);
+  assertTrue(o.__foreign_init__ === undefined);
+})();