chrome: Cleanup class/struct forward declarations

chrome/browser/chromeos/login/ui/login_display_host.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_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_UI_LOGIN_DISPLAY_HOST_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/callback_list.h"
 #include "chrome/browser/chromeos/customization/customization_document.h"
 #include "chrome/browser/chromeos/login/ui/login_display.h"
 #include "ui/gfx/native_widget_types.h"
 
-namespace views {
-class Widget;
-}  // namespace views
-
 namespace chromeos {
 
 class AppLaunchController;
 class AutoEnrollmentController;
 class LoginScreenContext;
 class OobeUI;
 class WebUILoginView;
 class WizardController;
 
 // An interface that defines OOBE/login screen host.
@@ skipping 79 matching lines @@
   virtual void StartDemoAppLaunch() = 0;
 
  protected:
   // Default LoginDisplayHost. Child class sets the reference.
   static LoginDisplayHost* default_host_;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_UI_LOGIN_DISPLAY_HOST_H_