Add a new 1-arg constructor to ParsedQuicVersions.
Follow-up CLs will use this new constructor.

PiperOrigin-RevId: 839917271
diff --git a/quiche/quic/core/quic_versions.h b/quiche/quic/core/quic_versions.h
index b15dd17..2ecd462 100644
--- a/quiche/quic/core/quic_versions.h
+++ b/quiche/quic/core/quic_versions.h
@@ -210,12 +210,28 @@
   return false;
 }
 
+QUICHE_EXPORT constexpr HandshakeProtocol HandshakeProtocolForTransportVersion(
+    QuicTransportVersion transport_version) {
+  if (VersionIsIetfQuic(transport_version)) {
+    return PROTOCOL_TLS1_3;
+  }
+  if (transport_version == QUIC_VERSION_46) {
+    return PROTOCOL_QUIC_CRYPTO;
+  }
+  return PROTOCOL_UNSUPPORTED;
+}
+
 // A parsed QUIC version label which determines that handshake protocol
 // and the transport version.
 struct QUICHE_EXPORT ParsedQuicVersion {
   HandshakeProtocol handshake_protocol;
   QuicTransportVersion transport_version;
 
+  constexpr explicit ParsedQuicVersion(QuicTransportVersion transport_version)
+      : handshake_protocol(
+            HandshakeProtocolForTransportVersion(transport_version)),
+        transport_version(transport_version) {}
+
   constexpr ParsedQuicVersion(HandshakeProtocol handshake_protocol,
                               QuicTransportVersion transport_version)
       : handshake_protocol(handshake_protocol),