chrome: Cleanup class/struct forward declarations

chrome/browser/ui/ash/multi_user/multi_user_window_manager_test.h

 // Copyright 2015 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_UI_ASH_MULTI_USER_MULTI_USER_WINDOW_MANAGER_TEST_H_
 #define CHROME_BROWSER_UI_ASH_MULTI_USER_MULTI_USER_WINDOW_MANAGER_TEST_H_
 
 #include "base/macros.h"
 #include "chrome/browser/ui/ash/multi_user/multi_user_window_manager.h"
 #include "components/signin/core/account_id/account_id.h"
 
+class Browser;
+
 // This is a test implementation of a MultiUserWindowManager which allows to
 // test a visiting window on another desktop. It will install and remove itself
 // from the system upon creation / destruction.
 // The creation function gets a |browser| which is shown on |desktop_owner|'s
 // desktop.
 class TestMultiUserWindowManager : public chrome::MultiUserWindowManager {
  public:
   TestMultiUserWindowManager(Browser* visiting_browser,
                              const AccountId& desktop_owner);
   ~TestMultiUserWindowManager() override;
@@ skipping 27 matching lines @@
   aura::Window* created_window_;
   // The location of the window.
   AccountId created_window_shown_for_;
   // The current selected active user.
   AccountId current_account_id_;
 
   DISALLOW_COPY_AND_ASSIGN(TestMultiUserWindowManager);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_MULTI_USER_MULTI_USER_WINDOW_MANAGER_TEST_H_