net: Update the include paths of base/string_piece.h to its new location.

net/dns/dns_response.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_RESPONSE_H_
 #define NET_DNS_DNS_RESPONSE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "base/time.h"
 #include "net/base/net_export.h"
 #include "net/base/net_util.h"
 
 namespace net {
 
 class AddressList;
 class DnsQuery;
 class IOBufferWithSize;
 
@@ skipping 128 matching lines @@
   // Iterator constructed after InitParse positioned at the answer section.
   // It is never updated afterwards, so can be used in accessors.
   DnsRecordParser parser_;
 
   DISALLOW_COPY_AND_ASSIGN(DnsResponse);
 };
 
 }  // namespace net
 
 #endif  // NET_DNS_DNS_RESPONSE_H_