Unify enum NextProto and enum AlternateProtocol.

net/socket/next_proto.h

Index: net/socket/next_proto.h
diff --git a/net/socket/next_proto.h b/net/socket/next_proto.h
index 0cce71ff4599b7dd32e7ef3b23ad1157230a55c7..24807587c04219560facec749657f2486f2f535f 100644
--- a/net/socket/next_proto.h
+++ b/net/socket/next_proto.h
@@ -7,6 +7,9 @@
 
 #include <vector>
 
+#include "base/strings/string_piece.h"
+#include "net/base/net_export.h"
+
 namespace net {
 
 // This enum is used in Net.SSLNegotiatedAlpnProtocol histogram.
@@ -22,6 +25,11 @@ enum NextProto {
 // 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_