chrome: Cleanup class/struct forward declarations

chrome/browser/download/download_prefs.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_DOWNLOAD_DOWNLOAD_PREFS_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PREFS_H_
 
 #include <set>
 
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "components/prefs/pref_member.h"
 
-class PrefService;
 class Profile;
 
 namespace content {
 class BrowserContext;
 class DownloadManager;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
@@ skipping 90 matching lines @@
 
 #if defined(OS_WIN) || defined(OS_LINUX) || defined(OS_MACOSX)
   bool should_open_pdf_in_system_reader_;
   bool disable_adobe_version_check_for_tests_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(DownloadPrefs);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PREFS_H_