Remove multipath_enabled from quic_config and quic_connection. No functional change expected.

net/quic/core/quic_connection.cc

Index: net/quic/core/quic_connection.cc
diff --git a/net/quic/core/quic_connection.cc b/net/quic/core/quic_connection.cc
index 04b0d20ff2f54283097311de22af923a67d88fec..6d0c4e7446d0890776d65a6cac3304c459b93937 100644
--- a/net/quic/core/quic_connection.cc
+++ b/net/quic/core/quic_connection.cc
@@ -259,7 +259,6 @@ QuicConnection::QuicConnection(QuicConnectionId connection_id,
       largest_received_packet_size_(0),
       goaway_sent_(false),
       goaway_received_(false),
-      multipath_enabled_(false),
       write_error_occured_(false),
       no_stop_waiting_frames_(false) {
   QUIC_DLOG(INFO) << ENDPOINT
@@ -307,10 +306,6 @@ void QuicConnection::SetFromConfig(const QuicConfig& config) {
       idle_timeout_connection_close_behavior_ =
           ConnectionCloseBehavior::SILENT_CLOSE;
     }
-    if (FLAGS_quic_reloadable_flag_quic_enable_multipath &&
-        config.MultipathEnabled()) {
-      multipath_enabled_ = true;
-    }
   } else {
     SetNetworkTimeouts(config.max_time_before_crypto_handshake(),
                        config.max_idle_time_before_crypto_handshake());
@@ -1314,7 +1309,7 @@ bool QuicConnection::ProcessValidatedPacket(const QuicPacketHeader& header) {
 
   // Multipath is not enabled, but a packet with multipath flag on is
   // received.
-  if (!multipath_enabled_ && header.public_header.multipath_flag) {
+  if (header.public_header.multipath_flag) {
     const string error_details =
         "Received a packet with multipath flag but multipath is not enabled.";
     QUIC_BUG << error_details;