deprecate -FLAGS_quic_reloadable_flag_quic_disable_version_34 and remove support for QUIC v34.

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 6873776c5c2a1e00f8422468c1e9989842d0bf60..fc88850272c805cc338fef3f5fc3b5bfe439eac0 100644
--- a/net/quic/core/quic_versions.cc
+++ b/net/quic/core/quic_versions.cc
@@ -52,10 +52,6 @@ QuicVersionVector FilterSupportedVersions(QuicVersionVector versions) {
       if (FLAGS_quic_reloadable_flag_quic_enable_version_36_v3) {
         filtered_versions.push_back(version);
       }
-    } else if (version == QUIC_VERSION_34) {
-      if (!FLAGS_quic_reloadable_flag_quic_disable_version_34) {
-        filtered_versions.push_back(version);
-      }
     } else {
       filtered_versions.push_back(version);
     }
@@ -76,8 +72,6 @@ QuicVersionVector VersionOfIndex(const QuicVersionVector& versions, int index) {
 
 QuicTag QuicVersionToQuicTag(const QuicVersion version) {
   switch (version) {
-    case QUIC_VERSION_34:
-      return MakeQuicTag('Q', '0', '3', '4');
     case QUIC_VERSION_35:
       return MakeQuicTag('Q', '0', '3', '5');
     case QUIC_VERSION_36:
@@ -114,7 +108,6 @@ QuicVersion QuicTagToQuicVersion(const QuicTag version_tag) {
 
 string QuicVersionToString(const QuicVersion version) {
   switch (version) {
-    RETURN_STRING_LITERAL(QUIC_VERSION_34);
     RETURN_STRING_LITERAL(QUIC_VERSION_35);
     RETURN_STRING_LITERAL(QUIC_VERSION_36);
     RETURN_STRING_LITERAL(QUIC_VERSION_37);