[wasm] Support wasm module structured cloning.

chrome/test/data/wasm/wasm_serialization_worker.js

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+onmessage = function(e) {
+    var compiled_module = e.data;
+    var instance = new WebAssembly.Instance(compiled_module);
+    if (typeof instance === "undefined") {

[jsbell, 2016/08/18 16:48:02]

nit: why not just `instance === undefined` ?

[Mircea Trofin, 2016/08/18 17:34:08]

Acknowledged.

[Mircea Trofin, 2016/08/18 23:02:59]

Done.

+        postMessage("error!");
+        return;
+    }
+    var entrypoint = instance.exports["increment"];
+
+    if (typeof entrypoint != "function") {

[jsbell, 2016/08/18 16:48:02]

nit: might as well be consistent and use !==

[Mircea Trofin, 2016/08/18 17:34:08]

Acknowledged.

[Mircea Trofin, 2016/08/18 23:02:59]

Done.

+        postMessage("error!");
+        return;
+    }
+
+    var ret = entrypoint(42);
+    if (ret != 43) {
+        postMessage("didn't get 43");

[jsbell, 2016/08/18 16:48:02]

Do you want a return after this postMessage too, so only one is ever sent?

[Mircea Trofin, 2016/08/18 17:34:08]

Acknowledged.

[Mircea Trofin, 2016/08/18 23:02:59]

Actually, don't need to post that string, can just return. This was a remnant
from earlier code.

+    }
+    postMessage(ret);
+}