Support alert nodes by introducing $descendant and !ttsProps.

chrome/browser/resources/chromeos/chromevox/cvox2/background/automation_predicate.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 ChromeVox predicates for the automation extension API.
  */
 
 goog.provide('AutomationPredicate');
 goog.provide('AutomationPredicate.Binary');
@@ skipping 37 matching lines @@
 /** @type {AutomationPredicate.Unary} */
 AutomationPredicate.link =
     AutomationPredicate.makeRolePredicate(
         chrome.automation.RoleType.link);
 
 /**
  * @param {chrome.automation.AutomationNode} node
  * @return {boolean}
  */
 AutomationPredicate.leaf = function(node) {
-  return !node.firstChild || node.children.every(function(n) {
-    return n.state.invisible;
-  });
+  return !node.firstChild ||
+      node.role == chrome.automation.RoleType.button ||
+      node.children.every(function(n) {
+        return n.state.invisible;
+      });
 };
 
 /**
  * @param {chrome.automation.AutomationNode} node
  * @return {boolean}
  */
 AutomationPredicate.leafWithText = function(node) {
   return AutomationPredicate.leaf(node) &&
       !!(node.attributes.name || node.attributes.value);
 };
 
 /**
  * @param {chrome.automation.AutomationNode} first
  * @param {chrome.automation.AutomationNode} second
  * @return {boolean}
  */
 AutomationPredicate.linebreak = function(first, second) {
   // TODO(dtseng): Use next/previousOnLin once available.
   var fl = first.location;
   var sl = second.location;
   return fl.top != sl.top ||
       (fl.top + fl.height != sl.top + sl.height);
 };