Make ChromeVox cursor robust to deleted nodes

chrome/browser/resources/chromeos/chromevox/cvox2/background/output.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 Provides output services for ChromeVox.
  */
 
 goog.provide('Output');
 goog.provide('Output.EventType');
@@ skipping 1236 matching lines @@
   },
 
   /**
    * @param {!cursors.Range} range
    * @param {cursors.Range} prevRange
    * @param {EventType|Output.EventType} type
    * @param {!Array<Spannable>} rangeBuff
    * @private
    */
   range_: function(range, prevRange, type, rangeBuff) {
+    if (!range.start.node || !range.end.node)
+      return;
+
     if (!prevRange)
       prevRange = cursors.Range.fromNode(range.start.node.root);
     var cursor = cursors.Cursor.fromNode(range.start.node);
     var prevNode = prevRange.start.node;
 
     var formatNodeAndAncestors = function(node, prevNode) {
       var buff = [];
       var outputContextFirst = localStorage['outputContextFirst'] == 'true';
       if (outputContextFirst)
         this.ancestry_(node, prevNode, type, buff);
@@ skipping 112 matching lines @@
    * @param {EventType|Output.EventType} type
    * @param {!Array<Spannable>} buff
    * @private
    */
   subNode_: function(range, prevRange, type, buff) {
     if (!prevRange)
       prevRange = range;
     var dir = cursors.Range.getDirection(prevRange, range);
     var node = range.start.node;
     var prevNode = prevRange.getBound(dir).node;
+    if (!node || !prevNode)
+      return;
+
     var options = {annotation: ['name'], isUnique: true};
     var startIndex = range.start.index;
     var endIndex = range.end.index;
     if (this.formatOptions_.braille) {
       options.annotation.push(new Output.NodeSpan(node));
       var selStart = node.textSelStart;
       var selEnd = node.textSelEnd;
       if (selStart !== undefined &&
           (selEnd >= startIndex && selStart <= endIndex)) {
         options.annotation.push(new Output.SelectionSpan(
@@ skipping 192 matching lines @@
           break;
         }
         earconFinder = earconFinder.parent;
       }
     }
     return null;
   }
 };
 
 });  // goog.scope