Delete "shutdown without closing browsers" path

ash/shell/shell_delegate_impl.h

 // 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.
 
 #ifndef ASH_SHELL_SHELL_DELEGATE_IMPL_H_
 #define ASH_SHELL_SHELL_DELEGATE_IMPL_H_
 
 #include <string>
 
 #include "ash/shell_delegate.h"
@@ skipping 21 matching lines @@
   void SetWatcher(WindowWatcher* watcher);
   void set_browser_context(content::BrowserContext* browser_context) {
     browser_context_ = browser_context;
   }
 
   virtual bool IsFirstRunAfterBoot() const OVERRIDE;
   virtual bool IsIncognitoAllowed() const OVERRIDE;
   virtual bool IsMultiProfilesEnabled() const OVERRIDE;
   virtual bool IsRunningInForcedAppMode() const OVERRIDE;
   virtual void PreInit() OVERRIDE;
-  virtual void Shutdown() OVERRIDE;
+  virtual void PreShutdown() OVERRIDE;
   virtual void Exit() OVERRIDE;
   virtual keyboard::KeyboardControllerProxy*
       CreateKeyboardControllerProxy() OVERRIDE;
   virtual content::BrowserContext* GetActiveBrowserContext() OVERRIDE;
   virtual app_list::AppListViewDelegate* CreateAppListViewDelegate() OVERRIDE;
   virtual ShelfDelegate* CreateShelfDelegate(ShelfModel* model) OVERRIDE;
   virtual ash::SystemTrayDelegate* CreateSystemTrayDelegate() OVERRIDE;
   virtual ash::UserWallpaperDelegate* CreateUserWallpaperDelegate() OVERRIDE;
   virtual ash::SessionStateDelegate* CreateSessionStateDelegate() OVERRIDE;
   virtual ash::AccessibilityDelegate* CreateAccessibilityDelegate() OVERRIDE;
@@ skipping 14 matching lines @@
   ShelfDelegateImpl* shelf_delegate_;
   content::BrowserContext* browser_context_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellDelegateImpl);
 };
 
 }  // namespace shell
 }  // namespace ash
 
 #endif  // ASH_SHELL_SHELL_DELEGATE_IMPL_H_