[wasm] Support wasm module structured cloning.

chrome/test/data/wasm/wasm_tests.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.
+
+// Utility function. Use this to return data back to the C++ test.
+function respondToTestHarness(data) {
+  if (!window.domAutomationController) {
+    console.log("ERROR: no automation controller available");
+    return;
+  }
+  window.domAutomationController.send(data);
+}
+
+var xhrReadyState_DONE = 4;

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

You can rely on XMLHttpRequest.DONE being defined in Chromium. :) But...

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

Oh! Nice!

why the "but"? Would we run these tests elsewhere? (honest question, not
familiar with chromium policies)

[jsbell, 2016/08/18 18:13:14]

Just that if you replace XHR with fetch() you don't need DONE. Apologies for
being vague.

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

Done.

+
+// Compile a module here, but instantiate it in a worker.
+// Tests serialization/deserialization.
+// The file incrementer.wasm is fetched from //v8/test/mjsunit/wasm. The
+// C test needs to setup the server to include that path.
+function test_instantiateInWorker() {
+  var req = new XMLHttpRequest();

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

... can you use fetch() here instead of XHR since it's more readable?

fetch('incrementer.wasm')
  .then(response => {
    if (!response.ok) throw new Error(response.statusText);
    return response.arrayBuffer;
  })
  .then(data => {
    let mod = ...
    ...
  })
  .catch(error => respondToTestHarness(error.message));

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

Acknowledged.

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

Done.

+  req.addEventListener('load', function(e) {
+    if (req.readyState === xhrReadyState_DONE) {
+      var data = req.response;
+      var mod = new WebAssembly.Module(data);
+      var worker = new Worker("wasm_serialization_worker.js");
+      worker.postMessage(mod);
+      worker.onmessage = function(event) {
+        respondToTestHarness(event.data);
+      }
+    }
+  });
+  req.addEventListener('error', function(e) {
+    respondToTestHarness('error: ' + e);
+  });
+  req.open('GET', 'incrementer.wasm', true);
+  req.responseType = 'arraybuffer';
+  req.send();
+}