Correctly ignore AXTree event creation change state for reparented nodes

chrome/browser/resources/chromeos/chromevox/cvox2/background/cursors.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 Classes related to cursors that point to and select parts of
  * the automation tree.
  */
 
 goog.provide('cursors.Cursor');
@@ skipping 273 matching lines @@
     newNode = newNode || this.node_;
     newIndex = goog.isDef(newIndex) ? newIndex : this.index_;
     return new cursors.Cursor(newNode, newIndex);
   },
 
   /**
    * Returns whether this cursor points to a valid position.
    * @return {boolean}
    */
   isValid: function() {
-    return this.node.role !== undefined;
+    return !!this.node.root;
   }
 };
 
 /**
  * A cursors.Cursor that wraps from beginning to end and vice versa when moved.
  * @constructor
  * @param {!AutomationNode} node
  * @param {number} index A 0-based index into this cursor node's primary
  * accessible name. An index of |cursors.NODE_INDEX| means the node as a whole
  * is pointed to and covers the case where the accessible text is empty.
@@ skipping 236 matching lines @@
   /**
    * Returns whether this range has valid start and end cursors.
    * @return {boolean}
    */
   isValid: function() {
     return this.start.isValid() && this.end.isValid();
   }
 };
 
 });  // goog.scope