Fix accessability for web notification tray.

ash/system/status_area_widget.cc

 // Copyright (c) 2012 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 "ash/system/status_area_widget.h"
 
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/shell_delegate.h"
 #include "ash/shell_window_ids.h"
@@ skipping 309 matching lines @@
   Init(params);
   set_focus_on_creation(false);
   SetContentsView(status_area_widget_delegate_);
   GetNativeView()->SetName("StatusAreaWidget");
 }
 
 StatusAreaWidget::~StatusAreaWidget() {
 }
 
 void StatusAreaWidget::CreateTrayViews(ShellDelegate* shell_delegate) {
+  AddSystemTray(shell_delegate);
   AddWebNotificationTray();
-  AddSystemTray(shell_delegate);
   // Initialize() must be called after all trays have been created.
   if (system_tray_)
     system_tray_->Initialize();
   if (web_notification_tray_)
     web_notification_tray_->Initialize();
   UpdateAfterLoginStatusChange(system_tray_delegate_->GetUserLoginStatus());
 }
 
 void StatusAreaWidget::Shutdown() {
   // Destroy the trays early, causing them to be removed from the view
   // hierarchy. Do not used scoped pointers since we don't want to destroy them
   // in the destructor if Shutdown() is not called (e.g. in tests).
   system_tray_delegate_.reset();
+  system_tray_ = NULL;
   delete system_tray_;
-  system_tray_ = NULL;
+  web_notification_tray_ = NULL;
   delete web_notification_tray_;
-  web_notification_tray_ = NULL;
 }
 
 void StatusAreaWidget::AddSystemTray(ShellDelegate* shell_delegate) {
   system_tray_ = new SystemTray(this);
   status_area_widget_delegate_->AddTray(system_tray_);
 
   if (shell_delegate) {
     system_tray_delegate_.reset(
         shell_delegate->CreateSystemTrayDelegate(system_tray_));
   }
@@ skipping 66 matching lines @@
          web_notification_tray_->IsMouseInNotificationBubble());
   }
   if (should_show_launcher != should_show_launcher_) {
     should_show_launcher_ = should_show_launcher;
     Shell::GetInstance()->shelf()->UpdateAutoHideState();
   }
 }
 
 }  // namespace internal
 }  // namespace ash