Add GetSystemNSSKeySlot, merge GetPrivateNSSKeySlot/GetPublicNSSKeySlot to GetPersistentNSSKeySlot.

chrome/browser/net/nss_context_linux.cc

Index: chrome/browser/net/nss_context_linux.cc
diff --git a/chrome/browser/net/nss_context_linux.cc b/chrome/browser/net/nss_context_linux.cc
index 38529ebedac035303177d8cfb49afea6d9660e95..5aa18e6bb64f8196a01154eef396c0c84d7fe332 100644
--- a/chrome/browser/net/nss_context_linux.cc
+++ b/chrome/browser/net/nss_context_linux.cc
@@ -11,14 +11,14 @@
 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(