Add GetSystemNSSKeySlot, merge GetPrivateNSSKeySlot/GetPublicNSSKeySlot to GetPersistentNSSKeySlot.

chrome/browser/net/nss_context_linux.cc

 // Copyright (c) 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.
 
 #include "chrome/browser/net/nss_context.h"
 
 #include "content/public/browser/browser_thread.h"
 #include "crypto/nss_util_internal.h"
 #include "net/cert/nss_cert_database.h"
 
 crypto::ScopedPK11Slot GetPublicNSSKeySlotForResourceContext(
     content::ResourceContext* context) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
-  return crypto::ScopedPK11Slot(crypto::GetPublicNSSKeySlot());
+  return crypto::ScopedPK11Slot(crypto::GetPersistentNSSKeySlot());
 }
 
 crypto::ScopedPK11Slot GetPrivateNSSKeySlotForResourceContext(
     content::ResourceContext* context,
     const base::Callback<void(crypto::ScopedPK11Slot)>& callback) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
-  return crypto::ScopedPK11Slot(crypto::GetPrivateNSSKeySlot());
+  return crypto::ScopedPK11Slot(crypto::GetPersistentNSSKeySlot());
 }
 
 net::NSSCertDatabase* GetNSSCertDatabaseForResourceContext(
     content::ResourceContext* context,
     const base::Callback<void(net::NSSCertDatabase*)>& callback) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
   return net::NSSCertDatabase::GetInstance();
 }