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

net/base/url_util.cc

 // Copyright 2013 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/base/url_util.h"
 
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/escape.h"
 
 namespace net {
 
 GURL AppendQueryParameter(const GURL& url,
                           const std::string& name,
                           const std::string& value) {
   std::string query(url.query());
 
@@ skipping 70 matching lines @@
           *out_value = "";
         }
         return true;
       }
     }
   }
   return false;
 }
 
 }  // namespace net