chrome: Cleanup class/struct forward declarations

chrome/browser/download/chrome_download_manager_delegate.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_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_
 #define CHROME_BROWSER_DOWNLOAD_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 17 matching lines @@
 class Profile;
 
 namespace content {
 class DownloadManager;
 }
 
 namespace extensions {
 class CrxInstaller;
 }
 
-namespace user_prefs {
-class PrefRegistrySyncable;
-}
-
 // This is the Chrome side helper for the download system.
 class ChromeDownloadManagerDelegate
     : public content::DownloadManagerDelegate,
       public content::NotificationObserver,
       public DownloadTargetDeterminerDelegate {
  public:
   explicit ChromeDownloadManagerDelegate(Profile* profile);
   ~ChromeDownloadManagerDelegate() override;
 
   // Should be called before the first call to ShouldCompleteDownload() to
@@ skipping 122 matching lines @@
 #endif
 
   content::NotificationRegistrar registrar_;
 
   base::WeakPtrFactory<ChromeDownloadManagerDelegate> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeDownloadManagerDelegate);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_CHROME_DOWNLOAD_MANAGER_DELEGATE_H_