Deprecate --gfe2_reloadable_flag_quic_utils_use_fast_incremental_hash.

net/quic/quic_utils.cc

 // 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.
 
 #include "net/quic/quic_utils.h"
 
 #include <ctype.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 38 matching lines @@
                       Uint128Low64(uhash);
   const uint8_t* octets = reinterpret_cast<const uint8_t*>(data);
   for (size_t i = 0; i < len; ++i) {
     xhash = (xhash ^ octets[i]) * kPrime;
   }
   return uint128(static_cast<uint64_t>(xhash >> 64),
                  static_cast<uint64_t>(xhash & UINT64_C(0xFFFFFFFFFFFFFFFF)));
 }
 #endif
 
+#ifndef QUIC_UTIL_HAS_UINT128
+// Slow implementation of IncrementalHash. In practice, only used by Chromium.
 uint128 IncrementalHashSlow(uint128 hash, const char* data, size_t len) {
   // kPrime = 309485009821345068724781371
   static const uint128 kPrime(16777216, 315);
   const uint8_t* octets = reinterpret_cast<const uint8_t*>(data);
   for (size_t i = 0; i < len; ++i) {
     hash = hash ^ uint128(0, octets[i]);
     hash = hash * kPrime;
   }
   return hash;
 }
+#endif
 
 uint128 IncrementalHash(uint128 hash, const char* data, size_t len) {
 #ifdef QUIC_UTIL_HAS_UINT128
-  return FLAGS_quic_utils_use_fast_incremental_hash
-             ? IncrementalHashFast(hash, data, len)
-             : IncrementalHashSlow(hash, data, len);
+  return IncrementalHashFast(hash, data, len);
 #else
   return IncrementalHashSlow(hash, data, len);
 #endif
 }
 
 bool IsInitializedIPEndPoint(const IPEndPoint& address) {
   return net::GetAddressFamily(address.address().bytes()) !=
          net::ADDRESS_FAMILY_UNSPECIFIED;
 }
 
@@ skipping 433 matching lines @@
                              24)) {
     // Subnet part does not change (here, we use /24), which is considered to be
     // caused by NATs.
     return IPV4_SUBNET_CHANGE;
   }
 
   return UNSPECIFIED_CHANGE;
 }
 
 }  // namespace net