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

net/quic/chromium/quic_stream_factory.h

Index: net/quic/chromium/quic_stream_factory.h
diff --git a/net/quic/chromium/quic_stream_factory.h b/net/quic/chromium/quic_stream_factory.h
index 661cfeb23ee6dcba3cfb4244d9c2be52189dfb8c..f1533d7e3caeb523b4fc5de6a9c4e02edd7c373c 100644
--- a/net/quic/chromium/quic_stream_factory.h
+++ b/net/quic/chromium/quic_stream_factory.h
@@ -207,7 +207,6 @@ class NET_EXPORT_PRIVATE QuicStreamFactory
       size_t max_packet_length,
       const std::string& user_agent_id,
       const QuicVersionVector& supported_versions,
-      bool enable_non_blocking_io,
       bool store_server_configs_in_properties,
       bool close_sessions_on_ip_change,
       bool mark_quic_broken_when_network_blackholes,
@@ -525,9 +524,6 @@ class NET_EXPORT_PRIVATE QuicStreamFactory
 
   const QuicVersionVector supported_versions_;
 
-  // Set if experimental non-blocking IO should be used on windows sockets.
-  bool enable_non_blocking_io_;
-
   // True if QUIC should be marked as broken when a connection blackholes after
   // the handshake is confirmed.
   bool mark_quic_broken_when_network_blackholes_;