Fix a chrome browser crash which occurs when launched as part of chrome frame...

chrome/browser/browser_accessibility_manager_win.cc

 // Copyright (c) 2010 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.
 
 #include "chrome/browser/browser_accessibility_manager_win.h"
 
 #include "chrome/browser/browser_accessibility_win.h"
 #include "chrome/browser/renderer_host/render_process_host.h"
 #include "chrome/browser/renderer_host/render_view_host.h"
 #include "chrome/common/render_messages.h"
@@ skipping 140 matching lines @@
 
 BrowserAccessibility* BrowserAccessibilityManager::UpdateTree(
     const webkit_glue::WebAccessibility& acc_obj) {
   base::hash_map<int, LONG>::iterator iter =
       renderer_id_to_child_id_map_.find(acc_obj.id);
   if (iter == renderer_id_to_child_id_map_.end())
     return NULL;
 
   LONG child_id = iter->second;
   BrowserAccessibility* old_browser_acc = GetFromChildID(child_id);
+  if (!old_browser_acc)
+    return NULL;
 
   if (old_browser_acc->GetChildCount() == 0 && acc_obj.children.size() == 0) {
     // Reinitialize the BrowserAccessibility if there are no children to update.
     old_browser_acc->Initialize(
         this,
         old_browser_acc->GetParent(),
         child_id,
         old_browser_acc->index_in_parent(),
         acc_obj);
 
@@ skipping 46 matching lines @@
   if ((src.state >> WebAccessibility::STATE_FOCUSED) & 1)
     focus_ = instance;
   for (int i = 0; i < static_cast<int>(src.children.size()); ++i) {
     BrowserAccessibility* child = CreateAccessibilityTree(
         instance, GetNextChildID(), src.children[i], i);
     instance->AddChild(child);
   }
 
   return instance;
 }