Add QUIC v39 which will be used to experiment with HTTP/2 stream...

net/quic/core/quic_versions.cc

Index: net/quic/core/quic_versions.cc
diff --git a/net/quic/core/quic_versions.cc b/net/quic/core/quic_versions.cc
index a01b9a0233248b234d74876276593dd20d75723c..6873776c5c2a1e00f8422468c1e9989842d0bf60 100644
--- a/net/quic/core/quic_versions.cc
+++ b/net/quic/core/quic_versions.cc
@@ -30,7 +30,14 @@ QuicVersionVector FilterSupportedVersions(QuicVersionVector versions) {
   QuicVersionVector filtered_versions(versions.size());
   filtered_versions.clear();  // Guaranteed by spec not to change capacity.
   for (QuicVersion version : versions) {
-    if (version == QUIC_VERSION_38) {
+    if (version == QUIC_VERSION_39) {
+      if (base::GetFlag(FLAGS_quic_enable_version_39) &&
+          FLAGS_quic_reloadable_flag_quic_enable_version_38 &&
+          FLAGS_quic_reloadable_flag_quic_enable_version_37 &&
+          FLAGS_quic_reloadable_flag_quic_enable_version_36_v3) {
+        filtered_versions.push_back(version);
+      }
+    } else if (version == QUIC_VERSION_38) {
       if (FLAGS_quic_reloadable_flag_quic_enable_version_38 &&
           FLAGS_quic_reloadable_flag_quic_enable_version_37 &&
           FLAGS_quic_reloadable_flag_quic_enable_version_36_v3) {
@@ -79,6 +86,8 @@ QuicTag QuicVersionToQuicTag(const QuicVersion version) {
       return MakeQuicTag('Q', '0', '3', '7');
     case QUIC_VERSION_38:
       return MakeQuicTag('Q', '0', '3', '8');
+    case QUIC_VERSION_39:
+      return MakeQuicTag('Q', '0', '3', '9');
     default:
       // This shold be an ERROR because we should never attempt to convert an
       // invalid QuicVersion to be written to the wire.
@@ -110,6 +119,7 @@ string QuicVersionToString(const QuicVersion version) {
     RETURN_STRING_LITERAL(QUIC_VERSION_36);
     RETURN_STRING_LITERAL(QUIC_VERSION_37);
     RETURN_STRING_LITERAL(QUIC_VERSION_38);
+    RETURN_STRING_LITERAL(QUIC_VERSION_39);
     default:
       return "QUIC_VERSION_UNSUPPORTED";
   }