Ash: Fix browser icon menu model lifetime

chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_browser.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 "chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_browser.h"
 
 #include "ash/wm/window_util.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "content/public/browser/notification_service.h"
 #include "ui/events/event_constants.h"
 
 ChromeLauncherAppMenuItemBrowser::ChromeLauncherAppMenuItemBrowser(
     const base::string16 title,
     const gfx::Image* icon,
     Browser* browser,
     bool has_leading_separator)
     : ChromeLauncherAppMenuItem(title, icon, has_leading_separator),
       browser_(browser) {
+  DCHECK(browser);
   registrar_.Add(this,
                  chrome::NOTIFICATION_BROWSER_CLOSING,
                  content::Source<Browser>(browser));
 }
+ChromeLauncherAppMenuItemBrowser::~ChromeLauncherAppMenuItemBrowser() {
+}
 
 bool ChromeLauncherAppMenuItemBrowser::IsActive() const {
   return browser_ == chrome::FindBrowserWithWindow(ash::wm::GetActiveWindow());
 }
 
 bool ChromeLauncherAppMenuItemBrowser::IsEnabled() const {
   return true;
 }
 
 void ChromeLauncherAppMenuItemBrowser::Execute(int event_flags) {
@@ skipping 15 matching lines @@
   switch (type) {
     case chrome::NOTIFICATION_BROWSER_CLOSING:
       DCHECK_EQ(browser_, content::Source<Browser>(source).ptr());
       browser_ = NULL;
       break;
 
     default:
       NOTREACHED();
   }
 }