Completely detach removed nodes.

chrome/renderer/resources/extensions/automation/automation_node.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.
 
 var AutomationEvent = require('automationEvent').AutomationEvent;
 var automationInternal =
     require('binding').Binding.create('automationInternal').generate();
 var exceptionHandler = require('uncaught_exception_handler');
 var IsInteractPermitted =
     requireNative('automationInternal').IsInteractPermitted;
@@ skipping 181 matching lines @@
 var schema = requireNative('automationInternal').GetSchemaAdditions();
 var utils = require('utils');
 
 /**
  * A single node in the Automation tree.
  * @param {AutomationRootNodeImpl} root The root of the tree.
  * @constructor
  */
 function AutomationNodeImpl(root) {
   this.rootImpl = root;
+  this.hostNode_ = null;
   this.listeners = {__proto__: null};
 }
 
 AutomationNodeImpl.prototype = {
   __proto__: null,
   treeID: -1,
   id: -1,
   isRootNode: false,
 
+  detach: function() {
+    this.rootImpl = null;
+    this.hostNode_ = null;
+    this.listeners = {__proto__: null};
+  },
+
   get root() {
-    return this.rootImpl.wrapper;
+    return this.rootImpl && this.rootImpl.wrapper;
   },
 
   get parent() {
     if (this.hostNode_)
       return this.hostNode_;
     var parentID = GetParentID(this.treeID, this.id);
     return this.rootImpl.get(parentID);
   },
 
   get state() {
@@ skipping 677 matching lines @@
 
     obj = new AutomationNode(this);
     privates(obj).impl.treeID = this.treeID;
     privates(obj).impl.id = id;
     this.axNodeDataCache_[id] = obj;
 
     return obj;
   },
 
   remove: function(id) {
+    if (this.axNodeDataCache_[id])
+      privates(this.axNodeDataCache_[id]).impl.detach();
     delete this.axNodeDataCache_[id];
   },
 
   destroy: function() {
     this.dispatchEvent(schema.EventType.destroyed);
+    for (var id in this.axNodeDataCache_)
+      this.remove(id);
+    this.detach();
   },
 
   setHostNode(hostNode) {
     this.hostNode_ = hostNode;
   },
 
   onAccessibilityEvent: function(eventParams) {
     var targetNode = this.get(eventParams.targetID);
     if (targetNode) {
       var targetNodeImpl = privates(targetNode).impl;
@@ skipping 84 matching lines @@
 utils.defineProperty(AutomationRootNode, 'getOrCreate', function(treeID) {
   return AutomationRootNodeImpl.getOrCreate(treeID);
 });
 
 utils.defineProperty(AutomationRootNode, 'destroy', function(treeID) {
   AutomationRootNodeImpl.destroy(treeID);
 });
 
 exports.$set('AutomationNode', AutomationNode);
 exports.$set('AutomationRootNode', AutomationRootNode);