Fixes crash in BrowserAccessibilityManager destructor.

chrome/browser/browser_accessibility_manager.cc

 // Copyright (c) 2006-2008 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.h"
 
 #include "chrome/browser/browser_accessibility.h"
 #include "chrome/browser/render_process_host.h"
 #include "chrome/browser/render_widget_host.h"
 
 // The time in ms after which we give up and return an error when processing an
 // accessibility message and no response has been received from the renderer.
 static const int kAccessibilityMessageTimeOut = 500;
 
 // static
-BrowserAccessibilityManager* BrowserAccessibilityManager::Instance() {
+BrowserAccessibilityManager* BrowserAccessibilityManager::GetInstance() {
   return Singleton<BrowserAccessibilityManager>::get();
 }
 
 BrowserAccessibilityManager::BrowserAccessibilityManager()
     : instance_id_(0) {
   NotificationService::current()->AddObserver(this,
       NOTIFY_RENDERER_PROCESS_TERMINATED, NotificationService::AllSources());
 }
 
 BrowserAccessibilityManager::~BrowserAccessibilityManager() {
   // Clear hashmaps.
   instance_map_.clear();
   render_process_host_map_.clear();
 
-  NotificationService::current()->RemoveObserver(this,
-      NOTIFY_RENDERER_PROCESS_TERMINATED, NotificationService::AllSources());
+  // We don't remove ourselves as an observer because we are a Singleton object,
+  // and NotifcationService is likely gone by this point.
 }
 
 STDMETHODIMP BrowserAccessibilityManager::CreateAccessibilityInstance(
     REFIID iid, int iaccessible_id, int instance_id, void** interface_ptr) {
   if (IID_IUnknown == iid || IID_IDispatch == iid || IID_IAccessible == iid) {
     CComObject<BrowserAccessibility>* instance = NULL;
 
     HRESULT hr = CComObject<BrowserAccessibility>::CreateInstance(&instance);
     DCHECK(SUCCEEDED(hr));
 
@@ skipping 115 matching lines @@
   // Set BrowserAccessibility instance to inactive state.
   it->second->set_instance_active(false);
   render_process_host_map_.erase(it);
 
   // Delete entry also from InstanceMap.
   InstanceMap::iterator it2 = instance_map_.find(it->second->instance_id());
 
   if (it2 != instance_map_.end())
     instance_map_.erase(it2);
 }