chrome: Cleanup class/struct forward declarations

chrome/browser/ui/webui/chromeos/login/hid_detection_screen_handler.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_UI_WEBUI_CHROMEOS_LOGIN_HID_DETECTION_SCREEN_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_HID_DETECTION_SCREEN_HANDLER_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/values.h"
 #include "chrome/browser/chromeos/login/screens/hid_detection_view.h"
 #include "chrome/browser/ui/webui/chromeos/login/base_screen_handler.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "content/public/browser/web_ui.h"
 
-namespace base {
-class DictionaryValue;
-}
-
 namespace chromeos {
 
 class CoreOobeActor;
 
 // WebUI implementation of HIDDetectionScreenView.
 class HIDDetectionScreenHandler
     : public HIDDetectionView,
       public BaseScreenHandler {
  public:
 
@@ skipping 29 matching lines @@
   // Keeps whether screen should be shown right after initialization.
   bool show_on_init_;
 
   DISALLOW_COPY_AND_ASSIGN(HIDDetectionScreenHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_HID_DETECTION_SCREEN_HANDLER_H_