RefCounted types should not have public destructors, delegate cleanup

chrome/browser/extensions/webstore_installer.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_EXTENSIONS_WEBSTORE_INSTALLER_H_
 #define CHROME_BROWSER_EXTENSIONS_WEBSTORE_INSTALLER_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 27 matching lines @@
     // Inline installs trigger slightly different behavior (install source
     // is different, download referrers are the item's page in the gallery).
     FLAG_INLINE_INSTALL = 1 << 0
   };
 
   class Delegate {
    public:
     virtual void OnExtensionInstallSuccess(const std::string& id) = 0;
     virtual void OnExtensionInstallFailure(const std::string& id,
                                            const std::string& error) = 0;
+
+   protected:
+    virtual ~Delegate() {}
   };
 
   // Contains information about what parts of the extension install process can
   // be skipped or modified. If one of these is present, it means that a CRX
   // download was initiated by WebstoreInstaller. The Approval instance should
   // be checked further for additional details.
   struct Approval : public content::DownloadItem::ExternalData {
     static scoped_ptr<Approval> CreateWithInstallPrompt(Profile* profile);
     static scoped_ptr<Approval> CreateWithNoInstallPrompt(
         Profile* profile,
@@ skipping 90 matching lines @@
   // The DownloadItem is owned by the DownloadManager and is valid from when
   // OnDownloadStarted is called (with no error) until the DownloadItem
   // transitions to state REMOVING.
   content::DownloadItem* download_item_;
   int flags_;
   scoped_ptr<Approval> approval_;
   GURL download_url_;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_WEBSTORE_INSTALLER_H_