chrome: Cleanup class/struct forward declarations

chrome/browser/ui/webui/print_preview/sticky_settings.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 CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_STICKY_SETTINGS_H_
 #define CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_STICKY_SETTINGS_H_
 
 #include <memory>
 #include <string>
 
 #include "printing/print_job_constants.h"
 
 class PrefService;
 
-namespace base {
-class DictionaryValue;
-}
-
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 namespace printing {
 
 // Holds all the settings that should be remembered (sticky) in print preview.
 // A sticky setting will be restored next time the user launches print preview.
 // Only one instance of this class is instantiated.
 class StickySettings {
@@ skipping 10 matching lines @@
   void RestoreFromPrefs(PrefService* profile);
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
  private:
   std::unique_ptr<std::string> printer_app_state_;
 };
 
 }  // namespace printing
 
 #endif  // CHROME_BROWSER_UI_WEBUI_PRINT_PREVIEW_STICKY_SETTINGS_H_