Ash: Fix browser icon menu model lifetime

chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_browser.cc

Index: chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_browser.cc
diff --git a/chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_browser.cc b/chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_browser.cc
index 3f38fb4dfb4fac31fd7b702058dbaf17855c9159..26a75a8b145797767ae31c043b036c78eae39ace 100644
--- a/chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_browser.cc
+++ b/chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_browser.cc
@@ -20,10 +20,13 @@ ChromeLauncherAppMenuItemBrowser::ChromeLauncherAppMenuItemBrowser(
     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());