Revert of Unify enum NextProto and enum AlternateProtocol.

net/socket/next_proto.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 NET_SOCKET_NEXT_PROTO_H_
 #define NET_SOCKET_NEXT_PROTO_H_
 
 #include <vector>
 
-#include "base/strings/string_piece.h"
-#include "net/base/net_export.h"
-
 namespace net {
 
 // This enum is used in Net.SSLNegotiatedAlpnProtocol histogram.
 // Do not change or re-use values.
 enum NextProto {
   kProtoUnknown = 0,
   kProtoHTTP11 = 1,
   kProtoHTTP2 = 2,
   kProtoQUIC = 3,
   kProtoLast = kProtoQUIC
 };
 
 // List of protocols to use for NPN, used for configuring HttpNetworkSessions.
 typedef std::vector<NextProto> NextProtoVector;
 
-NET_EXPORT_PRIVATE NextProto
-NextProtoFromString(base::StringPiece proto_string);
-
-NET_EXPORT_PRIVATE const char* NextProtoToString(NextProto next_proto);
-
 }  // namespace net
 
 #endif  // NET_SOCKET_NEXT_PROTO_H_