mash: Fix content_browser shutdown crash if ash exits at the login screen

chrome/browser/chromeos/login/ui/login_display_host_impl.h

 // Copyright 2014 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 CHROME_BROWSER_CHROMEOS_LOGIN_UI_LOGIN_DISPLAY_HOST_IMPL_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_UI_LOGIN_DISPLAY_HOST_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 122 matching lines @@
   void OnDisplayMetricsChanged(const display::Display& display,
                                uint32_t changed_metrics) override;
 
   // Overriden from views::WidgetRemovalsObserver:
   void OnWillRemoveView(views::Widget* widget, views::View* view) override;
 
   // Overriden from chrome::MultiUserWindowManager::Observer:
   void OnUserSwitchAnimationFinished() override;
 
  private:
+  class LoginWidgetDelegate;
+
   // Way to restore if renderer have crashed.
   enum RestorePath {
     RESTORE_UNKNOWN,
     RESTORE_WIZARD,
     RESTORE_SIGN_IN,
     RESTORE_ADD_USER_INTO_SESSION,
   };
 
   // Type of animations to run after the login screen.
   enum FinalizeAnimationType {
@@ skipping 166 matching lines @@
 
   base::WeakPtrFactory<LoginDisplayHostImpl> pointer_factory_;
   base::WeakPtrFactory<LoginDisplayHostImpl> animation_weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(LoginDisplayHostImpl);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_UI_LOGIN_DISPLAY_HOST_IMPL_H_