Remove the unused "Disable non-blocking IO" QUIC experiment code.

net/http/http_network_session.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_HTTP_HTTP_NETWORK_SESSION_H_
 #define NET_HTTP_HTTP_NETWORK_SESSION_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 104 matching lines @@
     bool enable_http2_alternative_service;
 
     // Enables QUIC support.
     bool enable_quic;
     // Marks a QUIC server broken when a connection blackholes after the
     // handshake is confirmed.
     bool mark_quic_broken_when_network_blackholes;
     // Retry requests which fail with QUIC_PROTOCOL_ERROR, and mark QUIC
     // broken if the retry succeeds.
     bool retry_without_alt_svc_on_quic_errors;
-    // Use non-blocking IO for UDP sockets.
-    bool quic_enable_non_blocking_io;
     // Maximum number of server configs that are to be stored in
     // HttpServerProperties, instead of the disk cache.
     size_t quic_max_server_configs_stored_in_properties;
     // If not empty, QUIC will be used for all connections to the set of
     // origins in |origins_to_force_quic_on|.
     std::set<HostPortPair> origins_to_force_quic_on;
     // Source of time for QUIC connections.
     QuicClock* quic_clock;
     // Source of entropy for QUIC connections.
     QuicRandom* quic_random;
@@ skipping 186 matching lines @@
   NextProtoVector next_protos_;
 
   Params params_;
 
   std::unique_ptr<base::MemoryPressureListener> memory_pressure_listener_;
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_NETWORK_SESSION_H_