[Merge to 2881 for release cherry-picking] Re-enable the QUIC v33 hacks. protected by FLAGS_quic_re…

net/quic/core/quic_framer.cc

Index: net/quic/core/quic_framer.cc
diff --git a/net/quic/core/quic_framer.cc b/net/quic/core/quic_framer.cc
index b0dbe4ad6ae16ecea961902b0122a27900613820..bec9020c167156ee81e983e18588b225d834a0de 100644
--- a/net/quic/core/quic_framer.cc
+++ b/net/quic/core/quic_framer.cc
@@ -723,6 +723,11 @@ bool QuicFramer::AppendPacketHeader(const QuicPacketHeader& header,
     case PACKET_8BYTE_CONNECTION_ID:
       if (quic_version_ > QUIC_VERSION_32) {
         public_flags |= PACKET_PUBLIC_FLAGS_8BYTE_CONNECTION_ID;
+        if (!FLAGS_quic_remove_v33_hacks2 &&
+            perspective_ == Perspective::IS_CLIENT) {
+          public_flags |= PACKET_PUBLIC_FLAGS_8BYTE_CONNECTION_ID_OLD;
+        }
+
       } else {
         public_flags |= PACKET_PUBLIC_FLAGS_8BYTE_CONNECTION_ID_OLD;
       }