ChromeVox shouldn't navigate to iframe or webview elements.

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 150 matching lines @@
 /**
  * Non-inline textbox nodes which have an equivalent in the DOM.
  * @param {!AutomationNode} node
  * @return {boolean}
  */
 AutomationPredicate.leafDomNode = function(node) {
   return AutomationPredicate.leaf(node) ||
       node.role == RoleType.staticText;
 };
 
+
+/**
+ * Matches nodes that are containers that should be ignored during
+ * element navigation.
+ * @param {!AutomationNode} node
+ * @return {boolean}
+ */
+AutomationPredicate.ignoredContainer = function(node) {
+  return (node.role == RoleType.rootWebArea ||
+          node.role == RoleType.embeddedObject ||
+          node.role == RoleType.iframe ||
+          node.role == RoleType.iframePresentational ||
+          node.role == RoleType.embeddedObject);
+};
+
 /**
  * Matches against nodes visited during element navigation. An element as
  * defined below, are all nodes that are focusable or static text. When used in
  * tree walking, it should visit all nodes that tab traversal would as well as
  * non-focusable static text.
  * @param {!AutomationNode} node
  * @return {boolean}
  */
 AutomationPredicate.element = function(node) {
-  return (node.state .focusable && node.role != RoleType.rootWebArea) ||
+  if (AutomationPredicate.ignoredContainer(node))
+    return false;
+
+  return node.state.focusable ||
       (AutomationPredicate.leafDomNode(node) &&
        (/\S+/.test(node.name) ||
         (node.role != RoleType.lineBreak &&
          node.role != RoleType.staticText &&
          node.role != RoleType.inlineTextBox)));
 };
 
 /**
  * @param {!AutomationNode} first
  * @param {!AutomationNode} second
@@ skipping 37 matching lines @@
 
   return AutomationPredicate.leaf(node) &&
       (node.role == RoleType.client ||
        node.role == RoleType.div ||
        node.role == RoleType.group ||
        node.role == RoleType.image ||
        node.role == RoleType.staticText);
 };
 
 });  // goog.scope