Adjust wasm_serialization_tests.html the layout test to expect null on failure.

third_party/WebKit/LayoutTests/http/tests/wasm/wasm_serialization_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.
 
 function TestInstantiateInWorker() {
   return createWasmModule()
     .then((mod) => {
       var worker = new Worker("wasm_serialization_worker.js");
       return new Promise((resolve, reject) => {
         worker.postMessage(mod);
@@ skipping 39 matching lines @@
       for (var i = byteView.length - 1; i >= startOfWasmHeader + 3; --i) {
         if (byteView[i] != 0) {
           byteView[i] = 0;
           invalidated = true;
           break;
         }
       }
       assert_true(invalidated,
                   "the serialized blob should contain some non-null bytes.");
 
-      var deserialized = undefined;
-      try {
-        deserialized = window.internals.deserializeBuffer(byteView.buffer);
-        assert_unreached();
-      } catch (e) {
-        assert_equals(deserialized, undefined);
-      }
+      var deserialized = window.internals.deserializeBuffer(byteView.buffer);
+      assert_equals(deserialized, null);
     });
 }