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

net/cert/x509_certificate.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_CERT_X509_CERTIFICATE_H_
 #define NET_CERT_X509_CERTIFICATE_H_
 
 #include <string.h>
 
 #include <string>
 #include <vector>
 
 #include "base/gtest_prod_util.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/cert/cert_type.h"
 #include "net/cert/x509_cert_types.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <wincrypt.h>
 #elif defined(OS_MACOSX)
 #include <CoreFoundation/CFArray.h>
@@ skipping 475 matching lines @@
   // based on the type of the certificate.
   std::string default_nickname_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(X509Certificate);
 };
 
 }  // namespace net
 
 #endif  // NET_CERT_X509_CERTIFICATE_H_