Refactor client cert private key handling.

chrome/browser/ui/crypto_module_delegate_nss.h

 // Copyright 2013 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_UI_CRYPTO_MODULE_DELEGATE_NSS_H_
 #define CHROME_BROWSER_UI_CRYPTO_MODULE_DELEGATE_NSS_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/synchronization/waitable_event.h"
 #include "chrome/browser/ui/crypto_module_password_dialog.h"
 #include "crypto/nss_crypto_module_delegate.h"
 #include "net/base/host_port_pair.h"
 
 // Delegate to handle unlocking a slot or indicating which slot to store a key
 // in. When passing to NSS functions which take a wincx argument, use the value
 // returned from the wincx() method.
 class ChromeNSSCryptoModuleDelegate
     : public crypto::CryptoModuleBlockingPasswordDelegate {
  public:
   // Create a ChromeNSSCryptoModuleDelegate. |reason| is used to select what
   // string to show the user, |server| is displayed to indicate which connection
   // is causing the dialog to appear. |slot| can be NULL.
   ChromeNSSCryptoModuleDelegate(chrome::CryptoModulePasswordReason reason,
                                 const net::HostPortPair& server);
 
-  ~ChromeNSSCryptoModuleDelegate() override;
-
   // crypto::CryptoModuleBlockingPasswordDelegate implementation.
   std::string RequestPassword(const std::string& slot_name,
                               bool retry,
                               bool* cancelled) override;
 
  private:
+  friend class base::RefCountedThreadSafe<ChromeNSSCryptoModuleDelegate>;
+
+  ~ChromeNSSCryptoModuleDelegate() override;
+
   void ShowDialog(const std::string& slot_name, bool retry);
 
   void GotPassword(const std::string& password);
 
   // Parameters displayed in the dialog.
   const chrome::CryptoModulePasswordReason reason_;
   net::HostPortPair server_;
 
   // Event to block worker thread while waiting for dialog on UI thread.
   base::WaitableEvent event_;
 
   // Stores the results from the dialog for access on worker thread.
   std::string password_;
   bool cancelled_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeNSSCryptoModuleDelegate);
 };
 
 // Create a delegate which only handles unlocking slots.
 crypto::CryptoModuleBlockingPasswordDelegate*
     CreateCryptoModuleBlockingPasswordDelegate(
         chrome::CryptoModulePasswordReason reason,
         const net::HostPortPair& server);
 
 #endif  // CHROME_BROWSER_UI_CRYPTO_MODULE_DELEGATE_NSS_H_