chrome: Cleanup class/struct forward declarations

chrome/browser/download/chrome_download_manager_delegate.h

Index: chrome/browser/download/chrome_download_manager_delegate.h
diff --git a/chrome/browser/download/chrome_download_manager_delegate.h b/chrome/browser/download/chrome_download_manager_delegate.h
index 5fd0a258a03ad5a3652c1c0a66941088e8ab99cf..1091d3ed80f501c8c843ca7287c5fb12c581284f 100644
--- a/chrome/browser/download/chrome_download_manager_delegate.h
+++ b/chrome/browser/download/chrome_download_manager_delegate.h
@@ -35,10 +35,6 @@ namespace extensions {
 class CrxInstaller;
 }
 
-namespace user_prefs {
-class PrefRegistrySyncable;
-}
-
 // This is the Chrome side helper for the download system.
 class ChromeDownloadManagerDelegate
     : public content::DownloadManagerDelegate,