Provide skeleton for ChromeVox next.

chrome/browser/resources/chromeos/chromevox_next/chromevox2/background/background.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.
+
+/**
+ * @fileoverview The entry point for all ChromeVox2 related code for the
+ * background page.
+ */
+
+/** ChromeVox2 (ChromeVox Next) namespace */
+var cvox2 = function() {};
+
+/** Namespace for global objects in the background page. */
+cvox2.global = function() {};
+
+/** Classic Chrome accessibility API. */
+cvox2.global.accessibility =
+    chrome.accessibilityPrivate || chrome.experimental.accessibility;
+
+/**
+ * ChromeVox2 background page.
+ */
+cvox2.Background = function() {
+  // Only needed with unmerged ChromeVox classic loaded before.
+  cvox2.global.accessibility.setAccessibilityEnabled(false);
+  chrome.automation.getDesktop(this.onDesktopAvailable);
+};
+
+cvox2.Background.prototype = {
+  onDesktopAvailable: function(tree) {
+    if (!tree.root) {
+      window.setTimeout(this.onDesktopAvailable, 500);
+      return;
+    }
+    chrome.extension.onConnect.addListener(function(port) {
+      var cur = tree.root;
+      port.onMessage.addListener(function(message) {
+        switch (message.keydown) {
+          case 37:
+            cur = cur.previousSibling() || cur;
+            break;
+          case 38:
+            cur = cur.parent() || cur;
+            break;
+          case 39:
+            cur = cur.nextSibling() || cur;
+            break;
+          case 40:
+            cur = cur.firstChild() || cur;
+            break;
+        }
+        var index = 1;
+        if (cur.parent())
+          index = cur.parent().children().indexOf(cur) + 1;
+        var name = '';
+        if (cur.attributes && cur.attributes['ax_attr_name'])
+          name = cur.attributes['ax_attr_name'];
+        var utterance = index + ' ' + name + cur.role;
+        chrome.tts.speak(String(utterance), {lang: 'en-US'});
+      });
+    });
+  }
+};
+
+/** @type {cvox2.Background} */
+cvox2.global.backgroundObj = new cvox2.Background();