Refactor StringPiece hash.

net/dns/dns_hosts.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_DNS_DNS_HOSTS_H_
 #define NET_DNS_DNS_HOSTS_H_
 
 #include <stddef.h>
 
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/containers/hash_tables.h"
 #include "base/files/file_path.h"
 #include "net/base/address_family.h"
 #include "net/base/ip_address_number.h"
 #include "net/base/net_export.h"
 
 namespace net {
   typedef std::pair<std::string, AddressFamily> DnsHostsKey;
 };
 
 namespace BASE_HASH_NAMESPACE {
 
 template<>
 struct hash<net::DnsHostsKey> {
   std::size_t operator()(const net::DnsHostsKey& key) const {
-    hash<base::StringPiece> string_piece_hash;
-    return string_piece_hash(key.first) + key.second;
+    return base::StringPieceHash()(key.first) + key.second;
   }
 };
 
 }  // namespace BASE_HASH_NAMESPACE
 
 namespace net {
 
 // There are OS-specific variations in how commas in the hosts file behave.
 enum ParseHostsCommaMode {
   // Comma is treated as part of a hostname:
@@ skipping 40 matching lines @@
 // As above but reads the file pointed to by |path|.
 bool NET_EXPORT_PRIVATE ParseHostsFile(const base::FilePath& path,
                                        DnsHosts* dns_hosts);
 
 
 
 }  // namespace net
 
 #endif  // NET_DNS_DNS_HOSTS_H_