ChromeVox should not speak live regions that aren't in the document.

chrome/browser/resources/chromeos/chromevox/common/dom_util.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 A collection of JavaScript utilities used to simplify working
  * with the DOM.
  */
 
 
@@ skipping 175 matching lines @@
     return true;
   }
 
   return false;
 };
 
 
 /**
  * Checks the ancestor chain for the given node for invisibility. If an
  * ancestor is invisible and this cannot be overriden by a descendant,
- * we return true.
+ * we return true. If the element is not a descendant of the document
+ * element it will return true (invisible).
  * @param {Node} node The node to check the ancestor chain for.
  * @return {boolean} True if a descendant is invisible.
  * @private
  */
 cvox.DomUtil.hasInvisibleAncestor_ = function(node) {
   var ancestor = node;
   while (ancestor = ancestor.parentElement) {
     var style = document.defaultView.getComputedStyle(ancestor, null);
     if (cvox.DomUtil.isInvisibleStyle(style, true)) {
       return true;
     }
+    // Once we reach the document element and we haven't found anything
+    // invisible yet, we're done. If we exit the while loop and never found
+    // the document element, the element wasn't part of the DOM and thus it's
+    // invisible.
+    if (ancestor == document.documentElement) {
+      return false;
+    }
   }
-  return false;
+  return true;
 };
 
 
 /**
  * Checks for a visible node in the subtree defined by root.
  * @param {Node} root The root of the subtree to check.
  * @param {boolean} recursive Whether or not to check beyond the root of the
  *     subtree for visible nodes. This option exists for performance tuning.
  *     Sometimes we already have information about the descendants, and we do
  *     not need to check them again.
@@ skipping 2365 matching lines @@
         var describedNode = document.getElementById(describedById);
         if (describedNode) {
           desc += ' ' + cvox.DomUtil.getName(
               describedNode, true, true, true);
         }
       }
     }
   }
   return desc;
 };