Added background page loader component extension.

chrome/browser/resources/chromeos/backloader/web/cros_validator.js

+// Copyright (c) 2012 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 ChromeOSValidator() {
+}
+
+ChromeOSValidator.getInstance = function() {
+  if (!ChromeOSValidator.instance_) {
+    ChromeOSValidator.instance_ = new ChromeOSValidator();
+  }
+  return ChromeOSValidator.instance_;
+};
+
+ChromeOSValidator.prototype = {
+  LOADER_ORIGIN: 'chrome-extension://nbicjcbcmclhihdkigkjgkgafckdfcom',
+  LOADER_PAGE: '/background.html',
+  callback_: null,

[xiyuan, 2012/08/16 16:55:38]

nit: prefer to use undefined

[zel, 2012/08/16 17:17:22]

Done.

+
+  validate: function(callback) {
+    this.callback_ = callback;
+    var msg = { method: 'validate' };
+    window.parent.postMessage(msg,
+        this.LOADER_ORIGIN + this.LOADER_PAGE);
+  },
+
+  initialize: function() {
+    document.addEventListener('DOMContentLoaded', this.onPageLoad.bind(this));

[xiyuan, 2012/08/16 16:55:38]

This really depends on how ChromeOSValidator is integrated with the web. If the
web starts its work on DOMContentLoaded event, this might not work.

It seems that we could just move the logic in onPageLoad function here. And it
should work either way, i.e. no matter ChromeOSValidator.initialize is called in
a DOMContentLoaded handler or directly inlined in global scope.

[zel, 2012/08/16 17:17:22]

Done.

+  },
+
+  isValidMessage_: function(msg) {
+    return msg.origin == this.LOADER_ORIGIN;
+  },
+
+  onPageLoad: function(e) {
+    window.addEventListener('message', this.onMessage.bind(this), false);
+  },
+
+  onMessage: function(e) {
+    var msg = e.data;
+    if (msg.method == 'validationResults' && this.isValidMessage_(e)) {
+      if (this.callback_)
+        this.callback_(msg.os == 'ChromeOS');
+    } else {
+      console.log('#### ChromeOSValidator.onMessage: unknown message');
+      if (this.callback_)
+        this.callback_(false);
+    }
+  }
+};
+
+ChromeOSValidator.getInstance().initialize();