RefCounted types should not have public destructors, content/ remaining bits

content/public/browser/download_manager.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.
 //
 // The DownloadManager object manages the process of downloading, including
 // updates to the history system and providing the information for displaying
 // the downloads view in the Destinations tab. There is one DownloadManager per
 // active browser context in Chrome.
 //
 // Download observers:
@@ skipping 42 matching lines @@
 
 class BrowserContext;
 class DownloadManagerDelegate;
 class DownloadQuery;
 class DownloadUrlParameters;
 
 // Browser's download manager: manages all downloads and destination view.
 class CONTENT_EXPORT DownloadManager
     : public base::RefCountedThreadSafe<DownloadManager> {
  public:
-  virtual ~DownloadManager() {}
-
   static DownloadManager* Create(
       DownloadManagerDelegate* delegate,
       net::NetLog* net_log);
 
   // A method that can be used in tests to ensure that all the internal download
   // classes have no pending downloads.
   static bool EnsureNoPendingDownloadsForTesting();
 
   // Shutdown the download manager. Must be called before destruction.
   virtual void Shutdown() = 0;
@@ skipping 165 matching lines @@
 
   virtual bool GenerateFileHash() = 0;
 
   virtual DownloadManagerDelegate* delegate() const = 0;
 
   // For testing only.  May be called from tests indirectly (through
   // other for testing only methods).
   virtual void SetDownloadManagerDelegate(
       DownloadManagerDelegate* delegate) = 0;
 
+ protected:
+  virtual ~DownloadManager() {}
+
  private:
-  friend class base::RefCountedThreadSafe<
-      DownloadManager, BrowserThread::DeleteOnUIThread>;
-  friend struct BrowserThread::DeleteOnThread<BrowserThread::UI>;
-  friend class base::DeleteHelper<DownloadManager>;
+  friend class base::RefCountedThreadSafe<DownloadManager>;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_DOWNLOAD_MANAGER_H_