Set file tokens for NaCl main nexe if available to enable validation caching.

chrome/test/data/nacl/extension_validation_cache/extension_validation_cache.js

+// Copyright 2014 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 create(manifest_url) {
+  var embed = load_util.embed(manifest_url);
+
+  embed.addEventListener("load", function(evt) {
+    load_util.shutdown("1 test passed.", true);
+  }, true);
+
+  embed.addEventListener("error", function(evt) {
+    load_util.log("Load error: " + embed.lastError);
+    load_util.shutdown("1 test failed.", false);
+  }, true);
+
+  document.body.appendChild(embed);
+}
+
+function documentLoaded() {
+  create('extension_validation_cache.nmf');
+}
+
+document.addEventListener('DOMContentLoaded', documentLoaded);