Refactor client cert private key handling.

crypto/nss_crypto_module_delegate.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 CRYPTO_NSS_CRYPTO_MODULE_DELEGATE_H_
 #define CRYPTO_NSS_CRYPTO_MODULE_DELEGATE_H_
 
 #include <string>
 
+#include "base/memory/ref_counted.h"
+
 namespace crypto {
 
 // PK11_SetPasswordFunc is a global setting.  An implementation of
 // CryptoModuleBlockingPasswordDelegate should be passed using wincx() as the
 // user data argument (|wincx|) to relevant NSS functions, which the global
 // password handler will call to do the actual work. This delegate should only
 // be used in NSS calls on worker threads due to the blocking nature.
-class CryptoModuleBlockingPasswordDelegate {
+class CryptoModuleBlockingPasswordDelegate
+    : public base::RefCountedThreadSafe<CryptoModuleBlockingPasswordDelegate> {
  public:
-  virtual ~CryptoModuleBlockingPasswordDelegate() {}
 
   // Return a value suitable for passing to the |wincx| argument of relevant NSS
   // functions. This should be used instead of passing the object pointer
   // directly to avoid accidentally casting a pointer to a subclass to void* and
   // then casting back to a pointer of the base class
   void* wincx() { return this; }
 
   // Requests a password to unlock |slot_name|. The interface is synchronous
   // because NSS cannot issue an asynchronous request. |retry| is true if this
   // is a request for the retry and we previously returned the wrong password.
   // The implementation should set |*cancelled| to true if the user cancelled
   // instead of entering a password, otherwise it should return the password the
   // user entered.
   virtual std::string RequestPassword(const std::string& slot_name, bool retry,
                                       bool* cancelled) = 0;
+
+ protected:
+  friend class base::RefCountedThreadSafe<CryptoModuleBlockingPasswordDelegate>;
+
+  virtual ~CryptoModuleBlockingPasswordDelegate() {}
 };
 
 }  // namespace crypto
 
 #endif  // CRYPTO_NSS_CRYPTO_MODULE_DELEGATE_H_