Add VersionOfIndex() to quic_protocol.h

net/quic/core/quic_protocol.cc

Index: net/quic/core/quic_protocol.cc
diff --git a/net/quic/core/quic_protocol.cc b/net/quic/core/quic_protocol.cc
index 6b87945897085e047f28d136d11da8e21ca96c29..20e64fafd3276c4819b53ce549d10c196954a5ed 100644
--- a/net/quic/core/quic_protocol.cc
+++ b/net/quic/core/quic_protocol.cc
@@ -198,6 +198,17 @@ QuicVersionVector FilterSupportedVersions(QuicVersionVector versions) {
   return filtered_versions;
 }
 
+QuicVersionVector VersionOfIndex(const QuicVersionVector& versions, int index) {
+  QuicVersionVector version;
+  int version_count = versions.size();
+  if (index >= 0 && index < version_count) {
+    version.push_back(versions[index]);
+  } else {
+    version.push_back(QUIC_VERSION_UNSUPPORTED);
+  }
+  return version;
+}
+
 QuicTag QuicVersionToQuicTag(const QuicVersion version) {
   switch (version) {
     case QUIC_VERSION_30: